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.
Prototype : Easy Ajax and DOM manipulation for dynamic web applications
Wave.js : Audio visualizer library for javascript. Create dynamic animations that react to an audio file or audio stream.
SoundManager 2 : Using HTML5 and Flash, SoundManager 2 provides reliable cross-platform audio under a single JavaScript API.
A simple library for handling keyboard shortcuts in Javascript.