Meld is a visual diff and merge tool. It integrates with most version control systems. The diff viewer lets you edit files in place (diffs update dynamically), and a middle column shows detailed changes and allows merges. The margins show location of changes for easy browsing, and it also features a tabbed interface that allows you to open many diffs at once.
RepoManager offers a minimalistic approach to Web-based management of version control system repositories. Its goal is to simplify effective handling of repository permissions for a large number of users. Using RepoManager, users themselves are able to grant others permissions to use their repositories whenever they want.
repos-tools is a set of command-line utilities to make work on your code repositories faster and easier. It lets you push, pull, build, and do other things on your repositories all at once. The supported (D)VCSes are Git, Subersion, Bazaar, and Mercurial. For GitHub users, forking, following, watching, and dealing with issues can be done from the shell.