Having a few machines at my disposal I've decided to put them to good use and use my spare CPU time for two worthy causes:

Helping in the search for a Cure For Cancer.

Currently I have the following machines running the Cure For Cancer client (all running windows):

Athlon XP2000+, Athlon 1200, Athlon 800, Athlon 700, Duron 700

Searching for extraterrestrial life with SETI@Home.

And SETI is being run on these Linux machines:

Celeron 466, PentiumII 400, PentiumII 266.

While I love the idea of scouring the skys for signs of alien life, I do feel that helping to find a Cure For Cancer is a more worthy cause, which is why most of my processing power is devoted to that. If the people at United Devices produced a linux client for the Cure For Cancer program I would run that too. SETI is only getting CPU time from me because there is no Linux Cure For Cancer client.