This company hosts the "Volunteer Your PC" program that lets any PC owner participate in important research and development projects. Right now you can work on cancer research conducted by the Department of Chemistry at the University of Oxford. You can actually watch as your computer's unused processing power analyzes molecules that may help fight cancer, or even become a cure!
http://www.ud.com its from the makers of Seti@home, but much
better use of the CPU power if you ask me.
Gh0stFT