There are hundreds of AJAX Frameworks available. Most commonly used frameworks are jQuery, MooTools, Prototype, ASP.NET AJAX, Apache Wicket, Dojo Toolkit, DWR (Direct Web Remoting), Spry Framework, YUI (Yahoo User Interface) and Google Web Toolkit.
Here is a small description of these frameworks:
1. jQuery: The jQuery library is providing many easy to use functions and methods to make rich applications. These functions are very easy to learn and even a designer can learn it fast. Due to these features jQuery is very popular and in high demand among the developers. You can use jQuery in all the web based applications irrespective of the technology.
4. ASP.NET AJAX: The ASP.NET AJAX Control Toolkit is an open-source project built on top of the Microsoft ASP.NET AJAX framework. It is a joint effort between Microsoft and the ASP.NET AJAX community that provides a powerful infrastructure to write reusable, customizable and extensible ASP.NET AJAX extenders and controls, as well as a rich array of controls that can be used out of the box to create an interactive web experience.
5. Apache Wicket: Apache Wicket, commonly referred to as Wicket, is a lightweight component-based web application framework for the Java programming language conceptually similar to JavaServer Faces and Tapestry.
9. YUI (Yahoo User Interface) Library: It is a set of utilities and controls, for building richly interactive web applications using techniques such as DOM scripting, DHTML and Ajax BSD.