Donate your idle CPU time to medicine...
Two worthwhile distributed computing projects that I came across today are Folding@home and Genome@home.
The former seeks to understand the way in which proteins secondary and tertiary structures are formed, whilst the later seeks to use this information to derive novel genes (and hence proteins) for application in theraputic medicines.
If you have a computer on your desk, even if you use it throughout the day there is likely to be time when its full CPU capacity is not being used, and by downloading on of the clients you can help solve some of the computational problems that exist within medical research.