Engineering eggheads from the University of Cambridge have developed a system called ProFORMA (Probabilistic Feature-based On-line Rapid Model Acquisition), which is capable of turning any standard webcam into a pretty powerful 3D scanning tool. A video demonstration shows how it's done, which you can view here .
What's pretty amazing is that the 3D models are constructed in real-time as end-users slowly rotate objects with their hand in front of the webcam. The engineering team says the system works by "calculating the Delaunay tetrahedralisation of a point cloud obtained from online structure from motion estimation, which is then carved using a recursive and probabilistic algorithm to rapidly obtain the surface mesh."
Put more simply, the system generates and displays partial models of an object on the fly, which then allows the user to plan how to manipulate the object to generate additional views. The finished product is a 3D representation of the object that can then be tracked with rapid movements.