ZDNet have a quick start guide in Ed Burnette’s blog entry showing you how to get started with the Google Web Toolkit (GWT).
The GWT was annouced this year at JavaOne and gives Java developers a pure Java approach to developing AJAX applications, by converting the Java code into HTML and Javascript. The GWT gives you a Java API which will be familiar to Java developers, and allows you to develop your app using the provided Java components, and then when ready generate the HTML and Javascript representation of the app with AJAX functionality. This is an awesome approach to avoiding Javascript development, which is hard to debug and develop (in comparison with Java and the rich IDE tools available).