Today, I will give you three great references for working with JavaScript and the Document Object Model.

The JavaScript Cheat Sheet by AddedBytes

This page gives you a quick and easy overview of the main methods you will be using in JavaScript. Covers Regular expressions, Events, AJAX/XMLHttpRequest and other functions and methods that often come in handy. The whole cheat sheet even fits on a single A4 page, and can be printed out and hung next to your monitor.

The W3C DOM Introduction by Quirksmode

This document gives a very easily understandable overview and reference for the HTML DOM, and how to access and manipulate it from JavaScript.

and the DOM objects and methods overview by HowToCreate

This site provides a exhaustive list of all DOM methods available from JavaScript that have cross-browser support in the major browsers. It also uses color-coding to easily interpret the various calls, and how you can access them.

All of these are well worth skimming through to get an overview of the common JavaScript methods and the DOM.