I agree with Chris, it sounds like re-applying the thermal paste on the graphics card is probably the best thing to try.
Failing that, I would probably install Linux on it and use it as a headless server, maybe as a home file server. Laptops generally make nice servers because they draw relatively little power, and have a built-in battery backup.
If you're looking for something creative and relatively easy to do, you could install linux, install MPD (http://sourceforge.net/projects/musicpd/), load it up with music and attach it to your stereo for use as a network-attached jukebox. I've found Theremin (https://theremin.sigterm.eu/) to be a really nice MPD client for OS X. There are graphical and command-line clients available for most operating systems, and even clients for the iPhone/iPod touch and other smartphones.