Star Chart - Stellarium is a planetarium software that shows exactly what you see when you look up at the stars. It's easy to use, and free. Read more about Star Chart.
OpenSpace - OpenSpace is open source interactive data visualization software designed to visualize the entire known universe and portray our ongoing efforts to investigate the cosmos.
Google Sky Map - Google Sky Map is a free hand-held planetarium that allows you to identify stars, planets and more.
Celestia - Real-time 3D visualization of space
Code NASA - 253 NASA open source software projects
WorldWide Telescope - The WorldWide Telescope (WWT) is a Web 2.