script.aculo.us : script.aculo.us provides you with
easy-to-use, cross-browser user
interface JavaScript libraries to make
your web sites and web applications fly.
MooTools : MooTools is a compact, modular, Object-Oriented JavaScript framework designed for the intermediate to advanced JavaScript developer. It allows you to ...
Raphaël : Raphaël is a small JavaScript library that should simplify your work with vector graphics on the web. If you want to create your own specific chart or...
The Dojo Toolkit : Dojo saves you time and scales with your development process, using web standards as its platform. It’s the toolkit experienced developers turn to for...
A JavaScript framework for creating ambitious web applications