Gravel - [freeware - Windows] Models the interaction between bodies in space according to Newtonian physics. - http://www.rclsoftware.org.uk/gravel/
ChView - [Freeware - Win3.x/95] A three-dimensional aid to viewing some of the nearer stars of our galaxy, navigating the distances between them, and accessing basic stellar information. - http://members.nova.org/~sol/chview/
Copernic space simulator - 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. - http://www.regulus.ro/copernic/ecopernicus.htm
Liftoff Space Simulator - [commercial - Windows] Hands-on presentations and simulations about being an astronaut and commanding the space shuttle. - http://www.eti-tech.com
Gravity Simulator - [freeware - Win 9x/NT/2k/XP] Simulates orbits of planets and other celestial bodies. - http://www.orbitsimulator.com/gravity/articles/what.html
AstroFly - [freeware - Win 98/ME/2000/XP] Three-dimensional models of the Milky Way neighborhood. - http://www.anumajor.com/astrofly/index.html
StarStrider software 3D planetarium - [shareware - Win 98/ME/2K/XP] A 3D software planetarium. Photo realistic real-time 3D renderings of 2 million stars, galaxies, nebulae, and the Milky Way. Includes several educative tutorials. - http://www.starstrider.com/
Celestia - A free 3D space simulator that lets you travel through the solar system and beyond to over 100,000 stars. [Windows, Mac; Open source] - http://www.shatters.net/celestia/
SpaceWander Virtual Space Trip! - SpaceWander's award-winning multimedia tour of the Universe features real space pictures from NASA - http://www.spacewander.com
3D Solar System Simulator - A Java applet that shows an interactive 3D representation of the planets and satellites of the solar system. - http://www.inicia.es/de/avillanueva
GrandTour - Accurate wireframe simulator for the Voyager and Giotto space missions, with animation capability. Developed at JPL for science/navigation, and filmed by the BBC/NOVA. Conveniently runs from any Windows/DOS. Freeware. - http://www.faithreason.org/grandtour
Starry Night - [commercial - Win95/98/NT, Macintosh] A planetarium and solar-system simulator; lets you view the universe from anywhere in our planetary neighbourhood in the past, present, and future. - http://www.starrynight.com
Xstar N-body Solver - [open source - Unix] Displays results to the screen or can be used as a screen saver. Includes a college level introductory text on the n-body problem. - http://www.midwestcs.com/xstar/
Solar System Applet - [online Java applet] This 3-d solar system applet can be rotated and zoomed with the mouse. Below it are links to other online gravity simulators and resources for building solar system simulations. - http://www.burtleburtle.net/bob/physics/solar.html
OpenUniverse - [open source - Win95/98/NT/2000 or Unix/Linux & OpenGL] Newest NASA data creates a fast 3D display of our home solar system, 25000 stars, galaxy, planets, moons, asteroids and even controllable spacecraft. - http://www.openuniverse.org
Solar Kingdom - [commercial, demo available - Win95/98/NT] A solar system simulator and planetarium, with planetary encyclopaedia. - http://www.silverfrost.com