dumbsvnreview is a very simple frontend for performing code reviews with SVN. The idea is that you set it up with your repositories and your favorite graphical diff tool and specify the last revision of the last code review. It will then list every change since the last review through a Web interface.
CRET is a code review tool for reviewing and committing patches to a Subversion repository. It hooks into SVN's commit procedure and only performs the commit if the patch file has an "approved" status. When somebody wants to commit a patch file to an SVN repository, the patch file must first be added to CRET. The person committing must the select reviewers and enter an objective and title for the patch. This operation notifies the reviewers through email. A reviewer can add comments to a patch, approve it, or reject it. Comments are sent to the requestor via email. If a patch is approved, the requestor can commit the code. When the code is committed, email is sent to the requestor and reviewers for notification.