Java UI Toolkits (for the Web)
One thing that was big at JAX were these toolkits that allow Java developers to program user interfaces the way they're used to, by using libraries similar to SWT or Swing.
Two big ones I saw were Rich AJAX Platform (RAP), based on SWT, and wingS, based on Swing.
Now, Google has released the Google Web Toolkit (GWT). Not tightly based on a previous Java UI framework, GWT seems to be another good option for developing complex web user interfaces in Java.
These toolkits make things a lot easier for Java developers to make web user interfaces without having to master CSS and JavaScript. Java developers can stay in Java and have web interfaces generated for them. The result will be more rich web-based applications, something we will all benefit from.
Personally, I still have a lot of fun working with JavaScript and CSS by hand. I don't know if I'll ever start using one of these code-generating frameworks. I suspect those of us who have the patience and passion to put up with this stuff are in the minority.