Why not donate unused computer cycles to help Stanford Uni in it's fight against Cancer.
How it works: you install a program (there are various ones for older and for newer core 2 etc.) it then downloads a work order then disconnects from the net and processes that work using your computer while it is idle or just using a minimum amount of processes.
MORE INFO HERE
TSF have a team working on this project so why not give it a try
Details here;
Current Teams