This morning I had an email from Berkley University in Californi- aye-aye asking me if I was in any was dissatisfied with SETI@home, a screensaver service that downloads data in your own PC's idle time. Have a look at that highlighted link above!
I had switched this off over 10 months ago for no particular reason. The Search for Extra Terrestrial Intelligence (SETI) @home downloads a data packet from radio telescopes and your PC analyses it and sends it back to the University; in this way Berkley has millions and millions of PCs at its disposal to analyse radio data.
If the bit you return contains that magic message from Aliens getting in touch for a Friday pint, hey presto, you become world famous.
I have now reinstalled it!