Git-Flow is a collection of Git extensions to provide high-level repository operations for Vincent Driessen’s branching model.
You can get a brief introduction to Git in my article Getting started with Git.
Git-Flow can be found on GitHub: https://github.com/nvie/gitflow
Mark Derricutt made a short introduction to Git Flow:
Dave Bock made a screencast showing how to use Git-Flow:
Jeff Kreeftmeijer posted ‘Why aren’t you using Git-Flow?’