Javascript

irt.org

An excellent repository of javascript knowledge. What started out as a comp.lang.javascript FAQ has evolved into one of the most useful javascript sites on the Internet. Superbly organized.

Dynamic Drive

"...the #1 place on the net to obtain free, original DHTML & Javascripts to enhance your web site!" If you run a web site, then you need to know about Dynamic Drive.

Javascript Tutor

Javascript Tutor is a basic, yet intensive set of 25 lessons in Javascript programming. The student will get a firm grounding in a number of concepts and be ready to move on to more ambitious projects. This tutorial assumes no previous programming experience and contains many hands-on excercises designed to reinforce the topics covered.

MSDN (Microsoft Developer Network) JScript documentation

Microsoft's documentation. The MSDN website is very extensive and contains a massive amount of very useful information. Unfortunately, there are a few drawbacks. Navigating it is a little confusing... sort of like swimming through mud. It's got a Microsoft slant to it and the site seems to work best using Internet Explorer. Still, I recommend using it as a reference not only for javascript, but for other web development topics as well.

Javascript Kit - Complete JavaScript Reference

A very nicely done javascript reference. Well organized, simple, useful.

JavaScript Authoring Guide

This is the JavaScript documentation that came with the release of Netscape Navigator 3.0. It's a slightly older version (Javascript 1.1 as implemented in Netscape 3.0). I strongly recommend this documentation because one, it's simpler and vastly easier for the novice to use, and two, it documents mostly basic javascript that is easily digestible to any modern browser. I use it myself all the time as a quick and simple reference.