http://valleywag.com/tech/do+gooder/10-online-ways-to-save-the-world-244836.ph p

10. World Community Grid: When you're not using it, your computer can fight AIDS, muscular dystrophy, and cancer. After you download and install this program, the World Community Grid uses your computer's idle time to process data for any of several world-changing medical projects. WCG treats every computer as part of a giant processor: your computer downloads data, crunches it, and sends the info back to the Grid. If a crucial part of a medical cure is found using your computer, WCG will let you share the glory.