I was looking for a bug-tracking application the other night (yes, I write that many bugs into my programs that I need another program to keep them straight) andfound phpBugTracker. Very slick, PHP-based, and even works with PostgreSQL, which automatically earns brownie points with me (too many PHP coders/scripters think that mySQL is the only open source database in the world).
I looked at BugZilla, but I think that’s a bit heavyweight for my needs.