JAST (Javascript Toolkit) is an Open Source cross-platform javascript framework that aid users to perform the most hard operations with few simple lines of code.
It's modularity allow the download only for the code required to the page.
szTreeView is a javascript library to display data in tree structure. Features: code XHTML generated, AJAX capabilities (by using an independent small AJAX library), fully customizable. Shipped with JSP taglib and example webapp.