IBM has posted the first in a series of articles that will break down the basics of developing AJAX components using PHP and DHTML. This is a pretty good article, although it focuses on the bare basics: Ad boxes, Popups (tooltips), spinners, and tabs.
The Undersigned has posted a tutorial showing how to take an XHTML/CSS template and turn it into a Wordpress theme. This is an article I have been meaning to write for a long time myself, I just never got around to it.
Nonetheless it’s a good article but it will take some concentration to get through the entire thing thanks to The Undersigned’s skinny post layout - it makes reading articles as long as this one quite difficult.
I recommend a quick copy-paste into Word and format it into a much easier to read format.