Dutch researchers are trying to channel the energy of people in dance clubs into electricity to power said clubs. Here's a one-minute video from the BBC and National Geographic:
http://www.amazon.com/gp/blog/post/PLNK2N008M1UF3JRB via Glenn Reynolds
Definitely cool! I would love to see this kind of tech in subway platforms, sidewalks near busy areas, malls, and in a multitude of other places. Everyone walks so why not use the energy generated by it to power something? :)