pre-commit : A framework for managing and maintaining multi-language pre-commit hooks.
git-deploy : Straightforward, Heroku-style, push-based deployment. Your deploys can become as simple as this:
$ git push production master
gollum : A simple, Git-powered wiki with a sweet API and local frontend.
gitflow : Git extensions to provide high-level repository operations for Vincent Driessen's branching model.
Git Extensions is the only graphical user interface for Git that allows you control Git without using the commandline. It comes with a manual and video tutorials to get you started quickly.