The WorldWide Telescope - Microsoft Research
This is absolutely awe-inspiring.
When I was little, my favorite show was Carl Sagan's COSMOS on PBS (WGBH Channel 2, Boston). I even remember one day when I was sick, my mum brought a small TV into my room so I could still watch COSMOS that evening. Back then, I used to go to sleep and dream about the stars and nebula and everything else they used to show on that show.
One of the most compelling things about that show was the journey through space. It was nice, even given the primitive graphics of the time. It wasn't interactive, but it was great nonetheless.
Recently, I learned about the World-Wide Telescope project from Microsoft Labs. The project will not be online until the Spring, but you can see a great video of it in operation here. Now you can do your own journey through the universe.
It's hard not to be inspired by the images you see in something like this. From Microsoft:
The WorldWide Telescope (WWT) is a rich visualization environment that functions as a virtual telescope, bringing together imagery from the best ground and space telescopes in the world for a seamless, guided exploration of the universe.
WorldWide Telescope, created with Microsoft's high-performance Visual Experience Engine™, enables seamless panning and zooming across the night sky blending terabytes of images, data, and stories from multiple sources over the Internet into a media-rich, immersive experience.
This could be an amazing 10 foot experience as well. Might be time to finally hook a PC up to the HDTV downstairs.