Unit testing is an important part of a programmer’s toolbox and GWT has support built in with its class. Andrew Glover has written up a nice article on IBM Developerworks on how to unit test your GWT Applications using it. He starts off with a simple GWT example and shows how to refactor it to make it easier to test. Then he describes how to write the test case and run it. It’s a very imformative article.

The Ajaxian has just posted their review of the book .

This is not the reference “bible” for GWT, though it does contain more reference material in one place than any other source so far, so you’ll have to wait for that sort of reference work. But for anyone wanting to get a jump start on GWT, start developing applications, and understand what all the fuss is about, I heartily recommend this book.

Robert Hanson has put together a Google Maps-like widget called ViewportViewer.  It enables you to show a viewport of an image that is larger than the viewport itself.  The APIs are not final yet, but he’s looking for comments before its inclusion into the GWT-Widget Library. Looks really cool!
Demo