[Update]
While I haven't used it yet GitLab is looking promising. I believe that gitorious was bought out by GitLab. The free version is still missing things like LDAP support.
[Original]
gitorious + gerrit
or
gitolite + gerrit + git-web
If you're in the enterprise world - the open source options are lacking unless you have a dedicated scm manager or a small team. gitolite is very powerful, but doing things like managing users can be difficult.