Christian Heilmann's excellent guide to writing unobtrusive JavaScript. Takes the reader from the inline JavaScript world right through to a clean dynamically attached events with all the JavaScript code in external files. Covers DOM Scripting. This is the key reference to unobtrusive scripting.
Gez Lemon reviews Christian Heilmann's recently published book. Its a thumbs up, and recommended for developers working with standards and accessibility, regardless of their JavaScript level.