I just found a very interesting site, it’s called WorldWide Telescope.
WorldWide Telescope (WWT) enables your computer to function as a virtual telescope, bringing together imagery from the best ground and space-based telescopes in the world. Experience narrated guided tours from astronomers and educators featuring interesting places in the sky.
A web-based version of WorldWide Telescope is also now available. This version enables seamless, guided explorations of the universe from within a web browser on PC and Intel Mac OS X by using the power of Microsoft Silverlight 3.0.
There are new detailed Mars Exploration and Enhanced Night Sky images. You can also watch the Mars in a 3D View, just like Google Street View. It’s really worth a look.
Here is a sample Screenshot: