Review Board is a web-based tool designed to help projects and companies keep track of pending code changes and make code reviews much less painful and time-consuming. It is being developed for use in VMware, but is designed to be generic enough to use in any project. It currently has support for SVN, CVS, Perforce, Git, Bazaar, and Mercurial repositories.
Review Board is written using Django and Python.
Information on usage and installation can be found on http://www.reviewboard.org/docs/manual/dev/
General information on the project is available on http://www.reviewboard.org/