http://www.worldcommunitygrid.org/
It is like Folding@Home but more centralized.
That's a community that gave their computer idle CPU (when the computer is not used) to make calculation to help Health Research. You should really install the client, let it run, and forget it. For windows users, you can install this as a service and you can forget it. I've already install it at my job, I'm doing computer programming, and even when the software is compiling, I've never felt a slowdown in speed.
It would be a great help to everyone if you could install this, as those data really help researcher to find new treatment and things like that.
If you have any question feel free to ask, i'll try to answer with the best of my knowledge. You can also visit the forums.
At least, you should take a look at the website.
Thank you