So, I put something about this up on my facebook page earlier (for all you stalkers out there), but I thought I should put it here as well.
Folding @ Home is a project that the people at Stanford have put together to leverage the collective computing power of the Internet, and use users' PCs to conduct protein research related to a number of different diseases, like Parkinson's, Huntington's, Alzheimer's, and others. You sign up for it, download the program, which is pretty light weight, and then just let it run in the background. When you go to bed, or go to work for the day, the program makes use of both your CPU's computing power, as well as your GPU's, to conduct the research for the University.
The program can be resource heavy, however you have the option to turn it off while you're using the machine, or reduce the amount of resources allocated to it though a pretty simple interface.
It's a cool project, not all that unlike the Seti at Home project that has been going on for years and years now. You can also create a team, and then you can track your team's progress against other teams.
I've created a team, called TBOT for anyone who wants to join up with the program, the team number is 225317. The website is here: http://folding.stanford.edu/
*Note, I'm on another team right now, so the TBOT one is currently empty.*