As you can notice, I have created many threads asking questions about stuff done with AJAX. I love this language, it's so useful for creating different add-ons for your website.

I want to learn it since I find out about it about 2 weeks ago, but I don't know where to start. Do you have any idea?

I mainly use the Spry framework to build ajax scripts, it's a design oriented framework which makes ajax easy to use so you may find it useful.

http://labs.adobe.com/technologies/spry/

I made my own framework from scratch. packed in my WRS.

That is how easy to write AJAX. Honestly.