Another free offering by Google, and this time it is a product created by a company called Instantiations they acquired recently.
Now the products are being relaunched, free for developers, with the Google branding in place. The following four products are now available from Google free of charge:
WindowBuilder Pro is an application for developing GUI for Java applications, while WIndowTester Pro is for testing such UIs. CodePro AnalytiX is for automated code quality / security testing.
If you are into Java web development you can find out more about these tools and download them from the Google webtoolkit page on Google Code.