Astronomy
- Amazing Space - Space tours and visualization
- Celestia - Space Simulation - Free, but requires download. Get Add-ons at Celesita Motherload
- Google Sky
- Gunn Interactive Visualization of the Planets
- Moon Arounder
- Neave Online Planetarium
- Planet Quest Historic Timeline - (NASA)Scale of the Universe
- Search and Explore Mars (NASA)
- Sloan Digital SkyServer - Images of the universe
- Solar Estimation Tool
- Solar System Scope
- WorldWide Telescope - No need to download - run the Web Client