pepper is a commandline tool for retrieving statistics and generating reports from source code repositories. It ships with several graphical and textual reports, and is easily extensible using the Lua scripting language. It includes support for multiple version control systems, including Git and Subversion.
Git Manager is a Web interface for Git. It allows you to manage and create Git repositories, users, and access groups. It is based on Apache authentication mechanisms (HTTP or LDAP) and uses a MySQL database to store repo/user/group relation data. The ViewGit repository viewer is included.
gitolite is an access control layer on top of git. It allows you to setup git hosting on a central server, and have multiple "virtual" users (i.e., not "Unix" users) access multiple git repositories, with fine grained access control (read control at the repo level granularity, write control at branch/tag/file/dir level). It has several other features, comprehensive documentation, does not require root permissions, and does not depend on anything except git, Perl 5.8 or later, and any POSIX shell.