I've just figured out that BOINC is included in Fedora. I've been installing it manually and it's right there in the repos. Hooray less work!
Now, if you've never heard of BOINC, it's a distributed computing program which allows your unused processor cycles to be pressed into service for any one of several worthy projects doing anything from looking for a cure for cancer to looking for alien life. My personal favorite is the World Community Grid; it runs several other projects, mostly medical, alternatively. BOINC is great because it runs on everything - Linux, Mac OS, Windows, even the PS3!
The downside is that your processor will be active even when you're not doing anything on your computer, making it more of an energy draw. In my experience, the difference isn't all that big if you already leave your computer on.
The upside is that your processor will be contributing to valuable medical, climatological, or astrobiological (ok, astrobiology might not be terribly valuable) research. Think of it: if enough people get on, we could start predicting earthquakes and tsunamis much farther in advance, or cure malaria/dengue/cancer/aids. Isn't that worth a few processor cycles?
yum -y install boinc-client boinc-manager && boinc_client && boincmgr