From the IBM website:

The page-reload cycle presents one of the biggest usability obstacles in Web application development and is a serious challenge for Java™ developers. In this series, author Philip McCarthy introduces a groundbreaking approach to creating dynamic Web application experiences. Ajax (Asynchronous JavaScript and XML) is a programming technique that lets you combine Java technologies, XML, and JavaScript for Java-based Web applications that break the page-reload paradigm.

Good site on programming with ajax. Lots of examples and good code library to use. I like this site since it cuts thru the evangelical zealotry of many ajax sites and gives the good, the bad, and the ugly...

Code examples and links to other Ajax code sites.  Good example of popups like on the homepage...

Site with tutorials on xmlhttprequest, drag and drop, forms, uploaders, image gallery, live search, and tabbed pages.

A must page. 

Wow, Netvibes on acid. Very nice and slick interface to a bunch of feeds, flickrs, notes, and such. But the coolest thing is the iCal upload to the calendar widget.

Looks kind of fantastic. Certainly puts meetingmaker to shame in terms of clarity.