As a Natural Born Hacker, I tend to bounce around between a number of projects that I have brewing inside my head.
Although I'm ususally only working on solo projects, a versioning system is a tool that I couldn't live without. After using CVS for a number of years, I moved into the subversion camp, and now use subversion wherever I can.
A useful tool tied in with this is trac, which provides me with a web interface to my subversion repository, and also a handy wiki for making various notes.
If you feel inclined, why not browse my code repository?
These days I primarily write solutions in perl. Most of my projects should be in my code repository. You can read further information about some of these projects in my projects section.