DHTML and XmlHttpRequest References

Javascript References

Object Hierarchy and Inheritance in JavaScript - the best description of the OO nature of Javascript and inheritance in Javascript we've found

Dojo Toolkit An ambitious project started by the authors of several previous JS libraries. It aims to provide core utilities for XmlHttpRequest handling, event handling, accessibility / usability with back and forward button handling, etc. in addition to a set of rich UI widgets.
DWR Direct Web Remoting - provides data binding and serialization between Java and Javascript
Javascript Templates - allows you to define a text template much like Velocity, but in Javascript, then pass it the data to generate some text (HTML). Trimpath also has some other very cool stuff, but it's all GPL, whereas the JS Templates has been dual-licensed as Apache 2.0 as well.
JSON-RPC Exposes Java objects for simple XmlHttpRequest remote invocation.
Jsolait An OO framework for Javascript
Tool-man examples - Great examples including drag-n-drop sorting and edit in place.

The Ultimate JSP Tabs - Todd Ditchendorf's JSP taglib for tabbed panels and wizards
Nifty Corners - very cool DHTML combination of CSS and Javascript to produce rounded corners without graphics. Also see More Nifty Corners.
Using the XmlHttpRequest Object - one of the original articles on using XHR.
Dynamic HTML and XML Another article on XHR from Apple
Registering callbacks - examples of how to register callbacks for XmlHttpRequests
Colorizing Java sources using Javascript and CSS - Interesting example of using Javascript and CSS to modify page content
Fade Anything Technique Highlight changed items on a page with a colored background which fades away. See also the original Yellow Fade Technique.