You don’t have to search very hard to find educators and policy makers worried about the current condition of science, technology, engineering and mathematics (STEM) education in the United States.

There’s a STEM Education Coalition, a National Science Board STEM Education Commission, a Journal of STEM Education and even a STEMEd Caucus in Congress dedicated to passing legislation that increases funding for STEM education.

Organizations like these frequently cite statistics which show that American students lag behind their international counterparts.

For example, in the 2007 Trends in International Science and Math Study (TIMS), U.S. fourth graders placed eleventh in math and eighth in science, while U.S. eighth graders ranked ninth in math and eleventh in science.

Falling behind in these areas could eventually lead to a decline in American innovation, with drastic effects on the economy.

As a result, groups have recently taken a number of steps on local, regional, and national levels to improve interest and achievement in science and mathematics.

The open source community is also doing its part to improve STEM education.

They’ve created dozens of quality open source apps that aid both teachers and researchers, raising the bar for STEM education.

In addition, a number of universities and other organizations have “open sourced” the content of their curriculum, making course materials available online.

This “OpenCourseWare” is becoming increasingly popular. In fact, MIT’s OpenCourseWare project alone had 9.6 million visitors in 2010, most of whom weren’t otherwise associated with the university.

For this list, we collected 50 open source tools – both software and other types of open source projects – that are helping to improve STEM education.

As always, feel free to note any significant projects we might have missed in the comments section below.

Open Source: Astronomy and Space Exploration

1.) Celestia

A perennial favorite, Celestia allows users to view the night skies from any point on earth at any time or to see how the sky would look from any point in the known universe.

The interface is simple to use, and it uses real telescope imagery of stars, planets, asteroids, and other objects in space whenever possible. Operating System: Windows, Linux, OS X.

2.) Stellarium

Stellarium is like having your own personal planetarium on your computer.

In fact, it’s such an accurate depiction of the night sky seen with the naked eye or simple binoculars that it’s used by many planetariums. Operating System: Windows, Linux, OS X.

3.) KStars

KStars offers the same functionality as Stellarium, plus some tools for amateur astronomers, like an observing list, FOV editor, altitude vs. time tool, and more.

It comes with a default catalog of all stars up to magnitude 8, but you can expand it with a catalog of stars up to magnitude 16. Operating System: Windows, Linux.

4.) PP3

An excellent tool for teachers, PP3 creates star charts that are detailed enough for use in PowerPoint presentations or books. Note that in order to use it, you will also need LaTeX. Operating System: Windows, Linux.

5.) Cartes du Ciel (Skycharts)

Another option for creating star charts, Cartes du Ciel uses data from 16 different catalogs.

Don’t let the French name scare you off—there’s plenty of English documentation. Operating System: Windows, Linux, OS X.

6.) Open Luna

If looking at pictures of the sky isn’t good enough for you, Open Luna is an open-source project dedicated to sending actual spacecraft into space and eventually the moon.

The group’s first mission is scheduled to launch next month. Operating System: N/A.

7.) DevelopSpace

DevelopSpace has an even more ambitious goal—developing the necessary technology to enable a one-way trip to Mars in the near future.

Students and others who get involved can contribute directly to solving the technical challenges posed by a mission to Mars. Operating System: N/A.

Open Source: Biology

8.) TreeView X

This app makes it easy to view and explore phylogenetic trees. In case you don’t know, a phylogenetic tree is a diagram that shows the evolutionary relationship between different species based on their characteristics. Operating System: Windows, Linux, OS X.

9.) TREE-PUZZLE

TREE-PUZZLE attempts to re-construct phylogenetic trees (see above) from molecular sequence data.

The files it creates can also be viewed with TreeViewX. Operating System: Windows, Linux, OS X.

Open Source: CAD

10.) BRL-CAD

For more than 20 years, BRL-CAD has been used extensively by the U.S. military to model weapons systems.

Its Web site describes it as a “cross-platform Open Source combinatorial Constructive Solid Geometry (CSG) solid modeling system that includes interactive 3D solid geometry editing, high-performance ray-tracing support for rendering and geometric analysis, network-distributed framebuffer support, image and signal-processing tools, path-tracing and photon mapping support for realistic image synthesis, a system performance analysis benchmark suite, an embedded scripting interface, and libraries for robust high-performance geometric representation and analysis.” Operating System: Windows, Linux, OS X, others.

11.) FreeCAD

This 3D CAD tool is designed for mechanical engineers and product design specialists.

It currently offers modules for 3D meshes, 2D drafting, CAD part design, raytracing, drawing, and CAM. Operating System: Windows, Linux, OS X.

12.) OpenSCAD

This software for creating 3D CAD models offers two modeling techniques: constructive solid geometry and extrusion of 2D outlines.

The Web site offers extensive advice and documentation for new users, as well as links to photos of interesting objects designed with OpenSCAD. Operating System: Windows, Linux, OS X.

13.) Archimedes

Most useful for architects and structural engineers, Archimedes can create both 2D and 3D designs similar to the better-known AutoCAD software.

Note that while it’s useable, the software is still in the early stages of development. Operating System: Windows, Linux, OS X.

Open Source: Chemistry

14.) Kalzium

Kalzium describes itself as “your digital replacement for the periodic table on paper.”

It displays information from the periodic table in a variety of ways, and it offers a molecular weight calculator, 3D molecule editor, an equation solver for stoichiometric problems and more.

(Note that in order to use Kalzium on Windows, you’ll need KDE for Windows.) Operating System: Windows, Linux.

15.) Jmol

Java-based Jmol gives you a 3D view of molecules with features for chemicals, crystals, materials and biomolecules.

In addition to the downloadable version, it’s also available as a Web app or in a development tool kit. Operating System: OS Independent.

Open Source: Earth Science

16.) Seismic Toolkit (STK)

If you’re studying recent earthquakes and tremors, this app makes it easier to plot and analyze seismographic data.

Note that while the app does run on Windows, it’s much faster on Linux. Operating System: Windows, Linux, OS X.

Open Source: Electronics

17.) gEDA

Short for GPL’d Electronic Design Automation tools, gEDA collects several related apps into a single suite.

It offers schematic capture, attribute management, bill of materials generation, netlisting, analog and digital simulation and printed circuit board (PCB) layout capabilities. Operating System: Linux, OS X.

Open Source: Flashcards

18.) FlashQard

This memorization tool lets you create “different card types for different purposes,” such as maps for geography training, vocabulary cards for learning scientific terms, photo cards, etc.

It uses the Leitner System to present cards in an order that will optimize learning without wasting time on cards you already know. Operating System: Windows, Linux.

19.) The Mnemosyne Project

This project combines a flashcard app with a scientific research project into the nature of memory.

It integrates with LaTeX to display mathematical symbols, as well as supporting pictures and sounds.

You can also use pre-built card sets for computers, astronomy, medicine, biology, chemistry, mathematics, and more. Operating System: Windows, Linux, OS X, Android.

20.) Pauker

This Java-based flashcard app also uses the Leitner Method to exercise your ultra-short-term, short-term, and long-term memory.

Although most of the pre-existing card sets train you in a foreign language, it does offer some STEM-related sets for mathematics, chemistry and nursing. Operating System: OS Independent.

21.) Anki

With support for text, graphics, video, audio, or scientific markup, Anki makes it easier to learn almost any subject.

In addition to using it on your desktop, you can also use it on your iPhone, Android phone, or even your Nintendo DS. Operating System: OS Independent.

Open Source: Math

22.) Sage

Sage combines more than 100 open source math tools into a single package for studying elementary and advanced, pure and applied mathematics.

It does offer a GUI, but in order to truly understand and use the software well, you need to know the Python programming language. Operating System: Windows, Linux, OS X.

23.) Genius

The Genius Math Tool started out as a simple calculator, but offers many more capabilities, including matrix calculations/linear algebra, number theory, calculus, statistics, plotting, and more.

It also includes a complete programming language (GEL) and a GUI for researchers or developers who want to create new functions. Operating System: Linux, OS X.

24.) GraphCalc

“When in the course of computing events it becomes apparent that not all calculators are created equal, one must turn no further than to GraphCalc,” says this app’s Web site.

It performs all the functions you would typically find on a standalone graphing calculator—and then some.

“GraphCalc can be your first, last, and only line of offense against the mathematics that threaten to push you over the brink of insanity.

It slices, dices, shreds and purees functions that leave other calculators wondering what hit them.” Operating System: Windows, Linux.

25.) gnuplot

If you’re comfortable working from the command line, this app can help you graph data and functions in 2D or 3D.

You can see many examples of how it has been used at WikiMedia. Operating System: Windows, Linux, OS X.

26.) TTCalc

If you need to perform calculations with numbers that are too big for your regular calculator to handle, TTCalc can do the job for you.

In addition to the usual arithmetic functions, it lets you use trigonometric functions, inverse trigonometric functions, hyperbolic functions, inverse hyperbolic functions, logical operators, logarithms, and more. Operating System: Windows.

27.) TuxMath

For the junior set, this math game asks kids to save Tux the penguin’s igloo by solving math problems.

You can choose the type of problems, from simple number recognition up to multiplying and dividing both positive and negative numbers. Operating System: Windows, Linux, OS X.

28.) Maxima

This computer algebra system graphs in 2D and 3D and performs differentiation, integration, Taylor series, Laplace transforms, ordinary differential equations, systems of linear equations, polynomials, and sets, lists, vectors, matrices, and tensors.

Although it does have a bare-bones GUI for graphing, it runs best from the command line. Operating System: Windows, Linux, OS X.

29.) Kig

Part of the KDE Education Suite, Kig allows you to draw geometric shapes for inclusion in other documents, or to measure and explore figures for a geometry class.

(Note that in order to use Kig on Windows, you’ll have to download KDE for Windows.) Operating System: Windows, Linux.

30.) KBruch

For elementary students (and their parents who still struggle with fractions), KBruch attempts to make fractions fun with a series of games.

It offers arithmetic, comparison, conversion, factorization and percentage exercises. (Note that in order to use KBruch on Windows, you’ll have to download KDE for Windows.) Operating System: Windows, Linux.

31. GeoGebra

The award-winning math app combines tools for geometry, arithmetic, algebra, and calculus.

It’s not only useful for students, it also has a number of tools to help instructors create worksheets and other teaching aids suitable for all levels from elementary to university. Operating System: OS Independent.

32.) Octave

Originally created for an undergraduate course on chemical reactor design, GNU’s Octave is a high-level programming language for solving numerical computations.

It can solve common numerical linear algebra problems, find the roots of nonlinear equations, integrate ordinary functions, manipulate polynomials in various ways, and integrate ordinary differential and differential-algebraic equations. Operating System: OS Windows, Linux, OS X.

Open Source: OpenCourseWare

33.) OCW Consortium

This Web site contains links to free university-level courses from hundreds of colleges and universities around the world.

Well-known U.S. members offering classes through the site include Johns Hopkins, MIT, UC Berkeley, University of Michigan, Notre Dame and 46 others. Operating System: OS Independent.

34.) eduCommons

This content management system is designed to support OpenCourseWare free online classes available through the OCW Consortium and other sources.

It’s used by a number of organizations around the world, including Notre Dame, Novell, UMass, and others. Operating System: OS Independent.

35.) Khan Academy

You may have seen Salman Khan’s video tutorials on YouTube. He now offers his 1800+ videos and related exercises, many of which cover math and science topics, as an open-source Web app. Operating System: OS Independent.

Open Source: Physics

36.) Step

With this interactive physics simulator, you place some objects on the screen, add some physical forces, and then see how they interact.

It covers classical mechanics, particles, springs, gravitational and coulomb forces, collisions, molecular dynamics, and much more.

(Note that in order to use Step on Windows, you’ll have to download KDE for Windows.) Operating System: Windows, Linux.

37.) Open Source Physics

This project aims to bring computational physics and computer modeling to the undergraduate classroom.

Tools at the site include simulations, EJS modeling, curriculum packages and programming tools. Operating System: OS Independent.

38.) Tracker

Built on the Open Source Physics Java framework, Tracker combines videos of physics experiments with computer modeling.

Key features include object tracking, center of mass tracking, rotational motion data, interactive graphic vectors and more. Operating System: OS Independent.

39.) Physlets

“Physlet” is short for “Physics Applets.” This collection of Java-based applets demonstrates a variety of physical laws and for teachers and students. Operating System: OS Independent.

40.) Xoscope

Especially helpful for educators teaching lessons on sound, Xoscope turns any Linux PC into an oscilloscope. It can accept audio input from up to eight different channels. Operating System: Linux.

Open Source: Online education/eLearning

41.) Claroline

Available in 35 languages, Claroline is used by hundreds of organizations in 93 countries to facilities online learning.

It gives instructors the tools they need to manage documents and links, create online exercises, develop learning paths, coordinate group work, and much more. Operating System: Windows, Linux, OS X.

42.) Moodle

One of the best-known online education tools, Moodle boasts more than 18 million known users taking more than 4 million courses.

It supports both online and blended learning classes and is designed to support a social constructionist framework of education. Operating System: Windows, Linux, OS X.

42.) eFront

One of the most visually attractive of the online education suites, eFront offers a very easy-to-use interface.

In addition to the free community edition, it’s also available in paid education and enterprise editions that add more features and support. Operating System: Windows, Linux.

44.) ILIAS

ILIAS is used in 19 different countries by organizations that include Novell, United States Joined Forces Command (US JFCOM), NATO, and the Canadian Air Forces.

Its key features include course management, tests/assessments, standards compliance, strong authentication, webcasting, online surveys, and more. Operating System: Windows, Linux.

Open Source: Report Authoring

45.) WIKINDX

For students and researchers involved in writing papers individually or collaboratively, WIKINDX makes it easier to track quotations and notes.

It integrates with numerous content managements systems (including Moodle, MediaWiki, and WordPress) and supports a variety of bibliographic style guides. Operating System: OS Independent.

Open Source: Robotics

46.) The Player Project

The Player Project offers three separate pieces of software that enable robotics research: Player provides a network interface for controlling robots and sensors.

Stage simulates the interaction of robots in a 2D environment, and Gazebo simulations robotic interactions in a 3D environment. Operating System: Linux, Unix, OS X.

47.) NASA Vision Workbench

Developed by NASA’s Intelligent Robotics Group, Vision Workbench is a general purpose image processing and computer vision library that has been used to analyze images on the moon and Mars.

It’s most useful for robotics researchers and developers who have a good working knowledge of C++. Operating System: Windows, Linux, Unix, OS X.

Open Source: Testing

48.) TCExam

This app allows teachers to administer digital assessments (computer-based tests) that students can access from a wide variety of devices.

It’s Web-based and provides scheduling and reporting tools to assist the instructor. Operating System: OS Independent.

48.) iTest

Another computerized testing option, iTest uses a client-server setup. It asks instructors to first establish a database of questions and answers that can be categorized, grouped and flagged in various ways.

They can then design examinations which either use all of the questions provided or pull from the database according to criteria which they control. Operating System: Windows, Linux, OS X.

50.) Safe Exam Browser

This app aims to prevent cheating on digital exams by locking down the browsers in a digital classroom.

It prevents students from browsing the Web, using shortcuts, right clicking and switching to other applications while an exam is in progress. Operating System: Windows, OS X.