How to Add Simple Permissions into Your Simple App. Also, Thoughtbot Rules! // RailsTips by John Nunemaker
http://railstips.org/2009/4/20/how-to-add-simple-permissions-into-your-simple-app-also-thoughtbot-rules

I didn't realize the automatic boolean attributes part.

how to use mixins in Rails, with loads of useful stuff about testing at the end

Shoulda examples