Xgravity is a program for the simulation of 3D gravitational motion of n-bodies. It reads a file with the current state of the bodies, and displays the motion. It features a nice isometric perspective, Red-Green stereographics, and a stereographic perspective which allows you to see the trace in "real" 3D. There is a GTK GUI interface in development, which gives you the ability to perform basic operations with the system, like modifing objects, rotating, eliminating drift, and launching a simulation.
wmJupiter is a Window Maker applet which features the planet Jupiter. It allows you to keep track of the Great Red Spot and the current distance in astronomical units (AE). The four Gallileo moons (Io, Europa, Ganymede, and Calisto) are also displayed when they are near the planet.
The satpass script provides satellite visibility predictions, given the position of the observer and the NORAD element sets for the desired satellites. It can acquire the NORAD element sets directly from any site supported by Astro::SpaceTrack. It can acquire the observer's latitude and longitude from http://geocoder.us/, look up star positions in the SIMBAD catalog, and more.
COSMIX is a general purpose N body integrator. It allows simulation of the behavior of gravitational systems according to different physical theories. The current release is only a test release - it only supports the newtonian approximation. The project aims at tackling relativity in coming releases.
ccurve_create.tcl is a TCL script (plus associated csh scripts) that makes it is possible to calculate cooling curves (plasma emissivities, in units of erg cm^3 s^-1) as a function of plasma temperature using the hot plasma codes available in the XSPEC spectral fitting program. Element-or-line-specific cooling functions can also be created. These can be used in hydrodynamical simulations to assess the total cooling rate, calculate the luminosity in a specific wavelength/energy range, or more generally to calculate X-ray or UV line diagnostics.