"Further more, I don’t really find it necessary for the kind of work that we do. Our biggest product, Basecamp, is about 10,000 lines of code. That really isn’t a whole lot in the grand scheme of things. Everything we do is build is also using Ruby on Rails, which means that most Rails programmers would know their way around our applications straight away. It’s the same conventions and patterns used throughout."
DHH at http://www.37signals.com/svn/posts/838-ask-37signals-how-do-you-document-code. Wish I could convince my boss of this… and he “programs” in Rails too.