I've marked our chef repo as public:
https://github.com/socallinuxexpo/scale-chef
It's by no means in perfect shape, but there's no secrets in it, there's contributing docs, and it's running the site, so no reason not to have it open to the world.
My co-workers were kind enough to help over the last few months whipping this all into shape. The goal of doing all the work we did to automate everything the site does in Chef was to make sure the setup was transparent, easy to see, and easy to contribute to. While it follows the Facebook model (which meant having to write very little code ourselves), which isn't the most common model in the Chef world, it is a well documented and used by a variety of organizations (not just FB), and most importantly, it makes making changes very simple.