This is one of those fun apps that you look to get real world usage from. Photosynth is a way of taking many photos to create a stitched together in a full 360-degree panorama.
The nice thing about Photosynth pictures is that they don’t just produce a horizontal strip, but they also stitch vertically, giving the full sensation of standing at a particular spot. The app includes geotagging, so you can effectively add Google Street View-style points anywhere you want. On top of being shareable on Bing Maps in that format, you can also share the photos on Facebook.
Photosynth has been used on the web for awhile now in some pretty interesting ways. Their engine has chewed through a bunch of community photos, found the common elements, and identified where the picture was shot. When you take popular subjects like the Notre Dame Cathedral, this can effectively provide a full 3D tour of a subject built using stitched photos