Links to free astronomy-related applications: Astronomy Stellarium Kstars Microsoft World Wide Telescope Halo Northern Sky Starcalc Skychart Celestia Celestia Extras Digital Universe Virtual Moon Atlas Where is M13? Starplot gSky Digest SaVi Universe Sandbox (Note: not free) Gravit Real data viewers Virtual Lab (microscopy) NASA WorldWind Nasa WorldWind extras Nasa WorldWind extras II (some might not work in the recent version of WorldWind) Virtual field trip (geology) Mission modelling AGI viewer Data sets (search for the links to vdf files, see "space exploration" and "space mission design and operations") Data sets (search for the links to vdf files, see "Interactive 3D Viewer files") Simulation of astronomical observations and analysis CLEA simulations Real data analysis Systemic (Analysis of radial velocity data of exoplanets) Galaxy classification Supernovae search Galactic mergers Solar storms search Simulation of space travel and planetary missions Orbiter Mars exploration games Web-based Sky-map Calsky.com (Astronomical ephemerides) Cassini Virtual Tour