BOINC

BOINC stands for Berkeley Open Infrastructure for Network Computing. For scientists it allows data intensive projects to be distributed to volunteers who allow access to their idle computing time. For you, the volunteer, it means participating in scientific research on astronomy, medicine, global warming and even searching for extraterrestrial intelligence. All you need to do is sign up, download the software and it operates behind the scenes using up spare computing capacity when you're busy doing something else.

Cool or what!!