free drag-and-drop GUI builder for Tk and Java from Sun
Tcl and Java Support: SpecTcl generates both Tcl and Java code.
Platform Independent: SpecTcl runs on all major platforms...
Constraint Based Alignment and resizing of widgets (buttons,
Geometry Manager: check boxes, etc.) is automatic. This makes
creating dynamic UIs and cross platform UIs a snap!
More infos and docu: http://sunscript.sun.com/products/spectcl.html
Cool stuff ! ;-)