Prototype - 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. - [Read more]

Open Rico - http://openrico.org/
An open-source Javascript library for creating rich internet applications. Rico provides full Ajax support, drag and drop management and a cinematic effects library. - [Read more]

Behaviour from bennolan - http://bennolan.com/behaviour/
Behaviour is the missing link for your ajax apps by using CSS to apply javascript behaviours. - [Read more]

moo.fx - http://moofx.mad4milk.net
moo.fx is a superlightweight, ultratiny, megasmall javascript effects library, written with prototype.js. It's easy to use, fast, cross-browser, standards compliant, provides controls to modify Height, Width, and Opacity with builtin checks that won't - [Read more]

dojo - dojo toolkit.org - http://dojotoolkit.org/
Dojo is the Open Source JavaScript toolkit that helps you build serious applications in less time. It fills in the gaps where JavaScript and browsers don't go quite far enough, and gives you powerful, portable, lightweight, and tested tools for constructi - [Read more]

SAJAX - http://absinth.modernmethod.com/sajax/
Sajax is an open source tool to make programming websites using the Ajax framework — also known as XMLHTTPRequest or remote scripting — as easy as possible. Sajax makes it easy to call PHP, Perl or Python functions from your webpages via Jav - [Read more]

xajax - http://www.xajaxproject.org/
Ajax-enable your PHP application with a simple toolkit that gets the job done fast. Runs on any PHP 4.3.x/PHP 5.x and Apache/IIS platform. - [Read more]

AjaxAC - http://ajax.zervaas.com.au/
AjaxAC is an open-source framework written in PHP, used to develop/create/generate AJAX applications. The fundamental idea behind AJAX (Asynchronous JavaScript And XML) is to use the XMLHttpRequest object to change a web page state using background HTTP s - [Read more]

CPAINT - http://cpaint.booleansystems.com/
CPAINT (Cross-Platform Asynchronous INterface Toolkit) is a multi-language toolkit that helps web developers design and implement AJAX web applications with ease and flexibility. - [Read more]

PAJAJ - http://pajaj.sourceforge.net/
What is the PAJAJ framework, it stands for (PHP Asynchronous Javascript and JSON). It is a object oriented Ajax framework written in PHP5 for development of event driven PHP web applications. - [Read more]