BOINC, the Berkeley Open Infrastructure for Network Computing is an open source middleware system for volunteer and grid computing.
It was originally developed to support the SETI@home project before it became useful as a platform for other distributed applications in areas as diverse as mathematics, medicine, molecular biology, climatology, and astrophysics.
The intent of BOINC is to make it possible for researchers to tap into the enormous processing power of personal computers around the world.