Getting Started with AJAX in jQuery
If you looking for some good tutorial to start learning AJAX with jQuery Developer Tutorial lunched great tutorial with good documented source code examples.
AJAX is probably the biggest thing you can add to your site; with AJAX, you can dramatically increase functionality, and give your end users more usable web applications. But AJAX is tricky to get started with - it usually requires very complex JavaScript knowledge. In this tutorial, I’ll show you how to get started with AJAX using the jQuery JavaScript framework.
In this article author describes how to make user authorization with AJAX and jQuery.