Yahoo! UI Library
http://developer.yahoo.net/yui/index.html
The Yahoo! User Interface Library is a set of utilities and controls, written in JavaScript, for building richly interactive web applications using techniques such as DOM scripting, HTML and AJAX. The UI Library Utilities facilitate the implementation of rich client-side features by enhancing and normalizing the developer's interface to important elements of the browser infrastructure (such as events, in-page HTTP requests and the DOM). The Yahoo UI Library Controls produce visual, interactive user interface elements on the page with just a few lines of code and an included CSS file. All the components in the Yahoo! User Interface Library have been released as open source under a BSD license and are free for all uses.
script.aculo.us
http://script.aculo.us/
The Web is changing. The 30-year-old terminal-like technology it was originally is gradually giving way to new ways of doing things. The power of AJAX allows for rich user interaction without the trouble that has bugged traditional web applications. Building upon the wonderful Prototype JavaScript library, script.aculo.us provides you with some great additional ingredients to mix in.
Prototype JavaScript Framework
http://prototype.conio.net/
Prototype is a JavaScript framework that aims to ease development of dynamic web applications. Featuring a unique, easy-to-use toolkit for class-driven development and the nicest Ajax library around, Prototype is quickly becoming the codebase of choice for web application developers everywhere.
http://openrico.org/
http://www.rubyonrails.com/
http://www.mochikit.com/
