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.
Mousetrap : A simple library for handling keyboard shortcuts in Javascript.
swfobject : SWFObject 2 offers two optimized Flash Player embed methods; a markup based approach and a method that relies on JavaScript & offers a JavaScript API ...
RequireJS : RequireJS is a JavaScript file and module loader. It is optimized for in-browser use, but it can be used in other JavaScript environments, like Rhino ...
A Modern, Lightweight Open-Source JavaScript Library for Interactive Maps