For those really wanting to learn JavaScript, I also recommend reading the Ecma 262 standard it is based upon:

http://www.ecma-international.org/publications/standards/Ecm...

It will help you understand how the core of the language works. I also keep the Mozilla Javascript Reference:

https://developer.mozilla.org/en/Javascript/Reference

handy for looking things up. For the browser compatibility side:

http://www.quirksmode.org/