Unfortunately, due to my complete inability to understand svn (know any good links for a single developer?)
I highly recommend Mercurial. I've tried multiple times to get SVN repositories set up and failed just as many times and never understood anything about it. But Mercurial is easy to understand and I set it up all by myself on my first try and have been using it successfully for about a week now, after I read about it in this thread. And it's great for a single developer because you don't actually need to host it on a server somewhere. Your repository is a directory on your computer.
For a quick (illustrated) overview on how Mercurial works: http://hginit.com/
To download and install: http://mercurial.selenic.com/
A couple free online repository hosting sites that offer Mercurial as an option:
http://bitbucket.org/ <- allows 1 private project and unlimited public (i.e. open source) projects with a maximum (total) space of 1 GB for free. Also comes with an issue tracker and wiki.
http://code.google.com/ <- only allows open source projects AFAIK
http://icculus.org/ <- You need to petition the owner for an account, and he's kind of picky, or so he says.
NOTE: Also similar to Mercurial is Git, but it has basically no support for Windows systems. See the DC thread on Git