Here are some basic depth camera interactivity I have been working on. In this test you can see particles being spawned on the users silhouette, the same again but with a speed cutoff, and a physical spline being drawn above the users silhouette to bounce cubes around. The idea is to provide some playful visual feedback for passers by, weather it be on a dance floor or as a part of an installation. They work to create a playful and exploratory space for the user to move in. Half the fun of this experiment is watching the strange and wacky movements people make while in front of it, it really seems to have a way of making people loosen up and be more outward with their movements.
You can see some footage of it in action @ Pausefest 2011 here