VSTrac is a Visual Studio addin which integrates Trac functionality into Visual Studio 2005 and 2008. It's main function is to facilitate management of tickets from within Visual Studio...
Collaboa is a Ruby web app inspired by Trac ... it features SVN Repository browsing and changeset viewing, as well as "issue" and milestone management. It's not as mature as Trac, but since it's written in Ruby it has a whole 'other audience.