A colleague of mine agreed to using Subversion (SVN) for our little project, but only if he doesn\'t have to install it. He has a U3 USB stick where he keeps the project fil
I was able to use the command line client that I had installed onto a USB stick. I then whipped up a couple batch files that did the basic checkout, checkin stuff, and one batch file that gave me a command prompt with a PATH set.
It doesn't have all the integration of something like TortoiseSVN, but I don't think you would be able to easily do that from a USB stick.