Wikipedia lists 20 current non-profit volunteer computing grids that use donated PC cycles to tackle grand challenge-type science problems,and 40 others in development. The latest, Charity Engine, embraces the ethically correct culture of volunteer computing and takes it to a new level: their computational power is sold to clients with a need for extra compute cycles (as in renting cloud-computing cycles).

Half of their proceeds are donated to the company’s select charities. The remaining half is distributed as prizes to lucky PC donors, chosen randomly. The PC’s compute cycles are harvested between keystrokes so the user is not normally aware that their system is being used.

Volunteer computing grids that use donated PC cycles to tackle grand challenge-type science problems are aided by BOINC (Berkeley Open Infrastructure for Network Computing), an open source grid framework that has made volunteer computing easy and cheap.