SpaceX Falcon 9 Lander - Try (and fail) to land Elon Musk's SpaceX rocket
Heavens Above - Website for tracking Satellites, Space ships and other space objects.
Universal Paperclips - Make paperclips not war
See A Satellite Tonight - Free web app to explore satellite locations.
Astronaut - You're an astronaut. Click to watch random videos in space.
Celestia - Real-time 3D visualization of space