WorldWide Telescope

From Microsoft:

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 Visual Experience Engine and allows seamless panning and zooming around the night sky, planets, and image environments. View the sky from multiple wavelenghts: See the x-ray view of the sky and zoom into bright radiation clouds, and then crossfade into the visible light view and discover the cloud remnants of a supernova explosion from a thousand years ago. Switch to the Hydrogen Alpha view to see the distribution and illumination of massive primordial hydrogen cloud structures lit up by the high energy radiation coming from nearby stars in the Milky Way. These are just two of many different ways to reveal the hidden structures in the universe with the WorldWide Telescope.

Choose from a growing number of guided tours of the sky by astronomers and educators from some of the most famous observatories and planetariums in the country. Feel free at any time to pause the tour, explore on your own (with multiple information sources for objects at your fingertips), and rejoin the tour where you left off. You can also create your own tours with music and voiceovers.