You're sat at your computer, playing freecell, and typing crap on a discussion board, and everything is ticking along quite nicely. Not much happening. The computer you're using is happily trickling along, using only a tiny fraction of it's power.
Well why not use that power?!?!!!
Be a part of something bigger!
As I'm typing this, my computer is trying to model the climate, and it's looking for signs of intelligent life in space.