Boinc

Boinc is a means for you to donate your unused computing time to various projects that you consider worthwhile. While you're browsing the web, reading/writing e-mails, writing letters/essays etc on a modern computer, typically only 5%-10% of the processing capacity of your computer is actually used.
Boinc sits in the background, taking up any spare processing capacity and giving it to various projects as determined by you. If Boinc detects that your computer suddenly starts to get used and needs that processing capacity, it will stop what it's doing, and give it to you. In other words, you won't even know it's there. I currently donate processing time to two projects,
Find out more about Boinc and the other projects you can support using it at, Boinc. Below are my contribution statistics, click on it for more details than you ever wanted.