What is Ajax?

Ajax, or AJAX, is a web development technique used for creating interactive web applications. The intent is to make web pages feel more responsive by exchanging small amounts of data with the server behind the scenes, so that the entire web page does not have to be reloaded each time the user requests a change. This is intended to increase the web page's interactivity, speed, functionality, and usability.

The name is an acronym standing for Asynchronous JavaScript and XML. Ajax is asynchronous in that loading does not interfere with normal page loading. JavaScript is the programming language in which Ajax function calls are made. Data retrieved using the technique is commonly formatted using XML, as reflected in the naming of the XMLHttpRequest object from which Ajax is derived.

Ajax is a cross-platform technology usable on many different operating systems, computer architectures, and Web browsers as it is based on open standards such as JavaScript and XML, together with open source implementations of other required technologies.

Below are a list of Ajax resources and tutorials

Prototype - http://www.prototypejs.com
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.
Script.alico.us - http://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. A great add-on for Prototype.
MooTools - http://mootools.net/
MooTools is a compact, modular, Object-Oriented JavaScript framework designed for the intermediate to advanced JavaScript developer. It allows you to write powerful, flexible, and cross-browser code with its elegant, well documented, and coherent API.
AjaxLoad - http://ajaxload.info/
Since the nature of how ajax doesn't reload the web browser, almost every application that uses an ajax framework needs a loading/processing image to represent that the browser is doing something.
MiniAjax - http://www.miniajax.com/
Here is a good resource for some simple ajax scripts that you can use how ever you want.