Satscape - A satellite tracking program for Windows, Mac OS and Linux.
NASA Exoplanet Posters - Imagine visiting worlds outside our solar system
Heavens Above - Website for tracking Satellites, Space ships and other space objects.
SpaceVR - Explore space with Oculus Rift (pre-launch)
Orbitron - Orbitron - Satellite Tracking System written by Sebastian Stoff.
Code NASA - 253 NASA open source software projects