Karsten announced a new version 4.0 of seaBreeze for Seaside.
In addition they now provide a QuickStart image - just download it and run and you are able to play with the software. Since it is a normal VisualWorks image you can just select "Browse" and "System" in the Launcher to browse the classes and find out how it is done. If you need more help just follow the mailinglist.
Compared to typical VisualWorks UI windowSpec the seaBreeze UI Builder now uses XML as storage format for the layouts. I like the XML integration into the VW Smalltalk IDE - they extended the Refactoring Browser with a new tab to browse the XML nodes. Nice.
It's not yet ported to Squeak/Pharo (the original Seaside platform) ... but at least there is some interest.