The WorldWide Telescope (WWT) is a Web 2.0 visualization software environment that enables your computer to function as a virtual telescope—bringing together imagery from the best ground and space-based telescopes in the world for a seamless exploration of the universe. WorldWide Telescope is created with the Microsoft high performance Visual Experience Engine™ and allows seamless panning and zooming around the night sky, planets, and image environments.

http://www.worldwidetelescope.org