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
If Java is available on the machines you could use SVNKit.
I may be very late to answer. Another alternative which may be acceptable to some users.
Eclipse IDE is portable (not entirely, it depends on Java). Use the Eclipse SVN plugin (Subversive or Subclipse). This takes care of the daily needs.
You may choose to point to a Java Portable installation to make it truly portable. However I believe it might be slow to run off a usb pen drive.
Finally, there is an PortableApps version of RapidSVN:
Try RapidSVN. The CollabNet binaries can be used in a similar fashion for command-line support. Yes, these have installers, but you can simply copy the binaries around -- I use Universal Extractor to get the binaries out without having to run the installer.
Also, an enterprising user has packaged RapidSVN as a PortableApp. There is an "installer", but it really just unzips things into a directory of your choice and writes a default configuration file into that directory.
There is a portable version of RapidSVN here. Just install it to a flash drive.