Space Simulation
Links
Gravity Simulator
http://www.orbitsimulator.com/gravity/articles/what.html
[freeware - Win 9x/NT/2k/XP] Simulates orbits of planets and other celestial bodies.
Liftoff Space Simulator
[commercial - Windows] Hands-on presentations and simulations about being an astronaut and commanding the space shuttle.
Copernic space simulator
http://www.geocities.com/fmarc83/paginigpu/ecopernicus.htm
A freeware program that lets you navigate through the solar system neighbourhood at different times in past or future, and to see the sky in a stereographic projection.