In a similar vein to the image-matching against point-clouds that was demonstrated in the Bing Maps TED talk, PhotoCity is aiming to progressively construct a 3D scan of the world. To this end they have released a free iPhone app that displays current scans, and encourages users to compete to fill in gaps in the scans. Currently there is a limited number of locations available to add to, but you may start your own “seeds”, which will create new areas to improve. I’m thinking of committing to a University of New South Wales seed – any helpers?
Edit: Still waiting for my building seed to be processed from this morning. The project is very new, so hopefully the delay is because they have a backlog, and not because they have abandoned processing new locations all together.