We are going to try using Trac at work. It's a software development tool that combines source control (via Subversion), bug/ticket tracking, and a wiki. It's easy to link patches to bugs, wiki pages to ticket queries, and tickets to wiki pages. It's written in Python and extensible with wiki macros written in Python.
At Kealia/Sun we managed to make this mostly work with Subversion, a source browser, Twiki, and Bugzilla.
I looked at Redmine which has more or less the same feature set--- better in a few areas. It's written in Ruby. But couldn't find a solid reason to prefer it. I just like the feel of Trac better.