Me 2!
Seeing the nice screenshot that Roman Kennke posted I wanted to post my own:
That is the Free Swing Demo from GNU Classpath Examples. Thanks to the hard work of David, Lillian, Roman and Tony Free Swing is really coming alive!
Hint: Adding more cool demos to GNU Classpath Examples will earn you instant fame (and lots of screenshot exposure). Plus it helps people starting out with Free Swing or other parts of the GNU Classpath library to see what and how things are possible (non-gui demos are also really appreciated).