I use http://www.codespaces.com, but I'm biased because I know the guy that founded and still runs it. It was the first app I saw that was fully written in Ext-js (this was pre 1.0) and back in 2007 or whenever it was that he wrote it it blew me away. It does all kinds of neat things, but mostly it's good because it's accessible to non-technical people -- lots of classic interface paradigms.

I also voted for Trac, because that's my go-to bug tracker for corporate projects that get checked in to a private SVN server.