Sorry for the blantant plug for my company's product, but the Oculus Layout Builder is really a great tool for super quick GUI building.
It uses a custom layout manager, so you would have to include a provided jar file when you run the code, but the layout manager really blows the other ones away. It is incredibly smart about stretching and sizing components. It is really easy to build GUIs that look and resize the way you want. You build the GUIs visually with drag and drop, and the generated code is very well organized.
It's not a full IDE, but it excels at making GUIs quickly and nicely. We use it internally when designing storyboards and GUIs for our other Java-based products, so I recommend it from personal use.
You can find out about it at
Oculus Layout System.
Bill
