It is a very impressive Proof Of Concept using your WebCam and Silverlight 4.0 :
Based on NyARToolkitCS library (ARToolkit).
[Link not working anymore : see my newer post on the 18th July 2010] With this one, you can choose your "enhanced" element (car, tank, ...) :
It uses the Hiro marker; more information on the Kodierer blog.
A lot of petential : Recognition of a 2D barcode, retrieves a contract (for instance), and enhances the display of that contract or add features on that contract.
Great stuff !