One of the more interesting projects at Microsoft's 'Live Labs' think tank is Photosynth, an application that can automatically transform images into a 3d representation of their location. Input every image of Trafalgar Square in London you can find on Flickr or Google and the application will generate a 3d world you can move through, or select individual images from to view.

There are several interesting uses of this, not only to combine images into 3d worlds but it also offers an interesting way to navigate through a set of images and explore environments. It's early in the project's development, but perhaps this offers a glimpse into the future of sites like Flickr, or applications like Picasa.
Check out the video tour.