I'm very happy with Redmine, and it's free. :) I do host it myself, which is really not very hard (my instance runs off a Ubuntu Server VM on my Windows work machine, and took about 30 mins to get running).
I just setup Redmine after seeing a comment about it here yesterday, took longer for the new subdomain to propagate than to install. In a day I have fully switched from a bunch of Trac installs since I can manage multiple projects with Redmine. Though I still think Trac's repo browsing is slightly better.
