The WorldWide Telescope is software created by Microsoft. It is a rich visualization environment that functions as a virtual telescope. It enables you to pan and zoom across the night sky blending terabytes of images, data, and stories from multiple sources. WorldWide Telescope has four categories of objects to look at Sky, Earth, Planets, and Panoramas. This software is freeware.

Homepage: http://www.worldwidetelescope.org