The time has come to talk about GUIs in the Software Engineering course I'm teaching currently, which led me to revisit using a GUI builder in Eclipse. (I will not hand-code a Swing GUI. I just won't.)
Previously I've used the Eclipse Visual Editor plugin, which, while not perfect, generally gets the job done. To my dismay, the current release of the VE does not work with the current stable release of Eclipse, and there has not been an official release of the VE since June 2006. (So sadly neglected / and often ignored / a far second to Belgium / when going abroad / Finland, Finland, Finland :-) I hope this project gets reinvigorated at some point, but I wasn't going to sit on my hands waiting for that to happen.
A quick google search turned up Jigloo, an Eclipse-based GUI builder which, while not free software, is gratis for non-commercial use. From my 10 minutes or so of using it, it appears to be very nice, quite a bit more polished than VE. We'll see how it goes, but I'm cautiously optimistic it will do what I need it to do.