Many Eclipse users think that Eclipse does not have an ergonomic plugin for Swing. Not at all .
1.Window Builder :
Pro is a great GUI Designer for eclipse and is now offered for free by google.
Google has recently given Windowbuilder pro to Eclipse. It's free and you can build swing, SWT and GWT screens. It's not totally mature but really worth trying.
2. JFormDesigner :
3.Visual Swing Designer for Eclipse