jQuery Annotated Source
Please Note: This project was released in 2011 when 1.6.2 was the latest jQuery version. It is no longer maintained.
I've gotten things started. If you're a jQuery nerd that knows the jQuery internals well and would like to help out, please fork and submit pull requests with your edits. The goal is to add documentation where comments are missing and replace terse comments with more readable, more natural language.
You can check it out here.
Questions/Comments? Hit up the Issues tab or find me on the Twitters at @robflaherty.