Frink is a calculating tool and programming language designed to help you in the real world. It tracks units of measurement throughout all calculations and ensures that answers are correct. It converts between systems of measurement, and has a huge library of physical data. It is both a simple calculator for quick calculations and a full-fledged programming language for large tasks. It draws high-quality graphics, handles conversions between time zones, currencies, and historical values of the U.S. dollar and the British pound, translates between several languages, does date/time math, and more.
Gpredict is a real time satellite tracking and orbit prediction program. Besides the general orbital data for satellites, gpredict can also calculate the footprint, visibility, doppler shift, signal loss, and signal delay for each satellite relative to one or more ground stations. The calculated data can be viewed in tables, on maps, or on polar graphs.
Astronomy for fun (education, science, whatever). Nightfall is an interactive application to simulate eclipsing binary stars, and to produce animated views, synthetic lightcurves and more. Takes into account the non-spherical shape of close binary stars, mutual reflection, and some other effects. Comes with documentation, on-line help, and lots of observational data of real binary stars. Supports the Gnome desktop, but doesn't require it.
Planets is a fun, interactive program for many-body gravity simulations. The emphasis is on play: it's easy to add in planets, zoom in and out, change the physical constants, save and load configurations, etc. It's designed to be easy enough for a kid to enjoy, but that hardly precludes adults.
Mars MOLA Viewer displays a fly-over rendering of the Martian surface, as measured by the Mars Global Surveyor, in real-time 3D animation. It downloads the Mars Orbiting Laser Altimeter topographic data files and uses them to drive the rendering. The user controls the position and the angle of the camera, and can move seamlessly over the entire Martian surface from -88 to 88 degrees latitude. It is a Java Web Start program with 1-click installation from your browser (depending on platform/browser).
PP3 creates celestial charts. It generates resolution-independent maps of very high graphical quality. They can be used, for example, as illustrations in books or on Web pages. It is possible to change many parameters, and arbitrary text can be placed on the maps. The output formats are EPS or PDF.
Asymptopia Flashcard System uses Motif and LaTeX to produce, manage, and use attractively formatted flashcards. You load some or all of your "collections" and set the timer for pop-up frequency. The GUI interface and "Collection Manager" make creating and modifying flashcards as simple as pushing a single button. A knowledge of LaTeX is only required when entering special symbols.
Open Source Astronomy is a comprehensive collection of astronomy software packages built for Linux, Mac OS X, and Windows. Each collection comprises approximately 5GB of software. An installation assistant is included along with a browsable documentation library covering all included packages.