When I was the VP of the Temple ACM, Tim Henry and I headed up an effort to get other ACMers to participate in the Folding@Home project. In short, this project is a way to donate spare CPU cycles to scientists working on computationally difficult problems.
A few weeks ago, I found myself bothered by how little I've put my Linode to use. For a while, I was using it quite a bit, and then life came along and gave me an upper-cut. So, I've decided to go back to donating CPU time to scientific projects. I'm using BOINC since it allows me to donate to several projects at once and has a pretty awesome Linux client.
If you have spare CPU time floating around, I'd encourage you to do the same!