Why not donate unused computer cycles to help Stanford University in it's fight against Cancer and other illness.
How it works: You install a small program (there are various ones for older and for newer core 2 etc.) it then downloads a "Work Unit" then disconnects from the net and processes that work using your computer while it is idle or just using a minimum amount of processes when finished it connects to the internet and sends the results and picks up more work
MORE INFO HERE
TSF has a team working on this project so why not give it a try
Details here:
Current TSF Teams