RightScale actively uses GitHub for hosting our Chef cookbook repositories that are used by our published ServerTemplates.
Below is a list of the most relevant cookbook repositories in RightScale's GitHub account.
A forked cookbook repository of opscode/cookbooks that are used by all RightScale ServerTemplates. It's necessary for RightScale to use a forked version of that repository in order to maintain a stable branch for development and test purposes.
Consolidated ('public-read') repository that includes the content that was previously found in the 'rightscale/cookbooks_public' and 'rightscale/cookbooks_premium' repositories. This repository is used by all LTS and infinity ServerTemplate releases published by RightScale.
A cookbook repository that includes a few cookbooks and recipes that are used by some of the Chef getting started tutorials.