I saw Trac being used by some projects recently. Decided to give it a try today for tracking a small prototyping project that I'm working on. It didn't take more than half an hour to get it running and it does its job without getting in the way. If you are looking for a bug tracker that's easy to set up and use, give it a try. It has an integrated wiki and source browsing tools (if you are using svn). I set it up to use SQLite and to run as a standalone server, which is the simplest way to get it running for a small project.