We started using a surplus laptop running linux as a CVS server 5 years ago. When that died, we replaced it with the cheapest netbook we could find. We hook that up via network to the programming computers.
Typically we only have 1 person making changes at competition (at most 2), but revision control is still very important (especially when you're asked to go back to the autonomous from 3 matches ago).
The next time our computer dies, I was planning to look into a plug computer like
SheevaPlug