a wonderful Eclipse plugin:
WindowBuilder, which can be used to develope Swing/SWT UI:
WindowBuilder is built as a plug-in to Eclipse and the various Eclipse-based IDEs (RAD, RSA, MyEclipse, JBuilder, etc.). The plug-in builds an abstract syntax tree (AST) to navigate the source code and uses GEF to display and manage the visual presentation.
Develop Java graphical user interfaces in minutes for Swing, SWT, RCP and XWT with WindowBuilder Pro's WYSIWYG, drag-and-drop interface. Use wizards, editors and intelligent layout assist to automatically generate clean Java code, with the visual design and source always in sync.
The project website: http://www.eclipse.org/windowbuilder/
To install the plugin in Eclipse: http://www.eclipse.org/windowbuilder/download.php
