Pyret
This document has detailed information on the Pyret grammar and the behavior of its expression forms and built-in libraries, along with many examples and some longer descriptions of language design choices. If you want to do something in a program and you can’t find how in this document, feel free to post a message on the Pyret discussion list, and we’ll be happy to help.
If you want to learn about (or teach!) programming and computer science using Pyret, check out Programming and Programming Languages (PAPL), which is a textbook on programming with all its examples in Pyret.