We just open sourced our company guidelines site! We previously kept the contents in a private wiki on GitHub, but I'm glad we finally put the time in giving the contents a real home.
As for why we decided to open source it all...
This site contains a set of guidelines we use to bring our projects to a good end. We decided to document our workflow because consistency is one of the most valuable traits of maintainable software.
The contents of this site exist for ourselves—more importantly, our future selves—and for giving future collegues a reference to our way of doing things and their quirks. The guidelines cover workflow, code style, and other little things we consider worth documenting.