http://www.redmine.org/
Redmine is a project management / bug tracker / etc written in Ruby on Rails. It supports multiple CVS back ends including SVN, CVS, Git, Mercurial, Bazaar and Darcs.
http://trac.edgewall.org/wiki/CommercialServices
The Trac wiki contains a list of commercial service providers including trac hosting companies. Useful resource for trac hosting.