Here are some screenshots of an older prototype which I haven't had time to update, but it still gives a good idea of how the widgets look in the IDE.
The next screenshot shows the same (older) prototype web application but deployed on a server and viewed in a browser. In this image, I hovered the mouse over "Goto" which caused a sub-menu of two web sites to slide out. Then, I moved the mouse over the "java.sun.com" sub-menu item, but the mouse does not show in the screenshot. Activating the item will go to that URL. This behavior was specified at design-time in the IDE.
If you're interested in learning more about the jMaki project and tools support and you will be in the neighborhood of San Francisco around the week of Monday, May 7, 2007 (ISO 2007-05-07), some of the key players will be speaking at JavaOne and CommunityOne. Even if you can't make it to JavaOne because of the cost, this year there is a free CommunityOne event that you can register for. For example, I did a search for Craig McClanahan and came up with this list of talks. You can also search for Greg Murray for jMaki talks and Ludo Champenois for other tools related talks.