Photosynth is an application which allows you to seamlessly traverse through a three dimensional space composed of digital photos.
The way they build these scenes is by processing a very large batch of images and comparing them looking for similarities, putting them together like a puzzle. I can't even begin to imagine how complex that algorithm must be.. The programmers must have had quite the trial and error phase.
I absolutely recommend you to try it out, it's the most innovative and useful web application I have seen for a very long time.
You can find the tech demo here:
http://labs.live.com/photosynth/
A final tip, try using your arrow keys to navigate the scene, was a whole lot easier than mouse interaction for me anyway.
This thread is probably out of place, but I couldn't find any place more suitable.