The Ajax experience brought together the foremost experts on the subject, take a look at the content and presentations given by some of these Ajax guru's in this post by Marc Grabanski.
Ben Galbraith - Co-founder of Ajaxian.com
Ben gave an overview of Ajax and started getting his hands right into some demo code. He showed a very basic implementation of the XMLHttpRequest object to send data to the server.
Tools to develop ajax are Aptana and Firebug - check and check. I absolutely love these tools and use them every day.
John Resig - Mozilla
* Level 1 - Easily drag and drop in widgets into your web application.
* Level 3 - Directly interact with the DOM API. Dealing directly with DOM and dealing directly with browser quirks and bugs.
Read Marc's entire post: