NATS by Example: A Simple Tutorial

The NATS by example.com website is a set of directories that are nested following the sort of URL hierarchy. And there's another section on every examples page that shows the actual output of the code that actually executed. Brett Victor has done some crazy things to tie those other ideas together, but probably more similar to things like blanking names or whatever. He says he was inspired by his own experience with writing tutorials and trying to make them easier to understand.