Another GUI Toolkit that has been on my todo list for sometime to look into is Prima. It is available for many platforms. Thier homepage is here:

http://www.prima.eu.org/

It looks quite nice but I do not yet have any experience with it. It does have an email list for help and discussion.

Another one I found while scrounging aroung was Guido at:

http://guido.sourceforge.net/

Again, don't know much about it, but it does look like it has seen no updates in the last couple years...