I found a nice Swing Designer for Eclipse called Visual Swing:
Eclipse Zone: Visual Swing for Eclipse
This is a project hosted on Google Code. So far, it has worked pretty nice. It is by no means a commercial solution, but it definitely gets the job done.
I had a little trouble installing it from the Update Site. The first time, I just downloaded the files and manually placed them in my Eclipse Home directory. But, today I figured out how to get the update site to work.
Here is the update site I had to use:
Then, in the install window, I had to uncheck “Group items by category”. Otherwise, it would say “There are no categorized items”. Finally, the install window seems to have a refresh problem. It was loading the items in the list, but it was not painting them. I had to give it some time to load, then I had to resize the install window to make it repaint the list.
There is an outstanding bug on the Update Site: Issue #119.