
I've experimented with most of the AJAX frameworks that have come out over the last year and ZK lives up to it's marketing line of, "Simple and Rich". ZK comes loaded with over 60 XUL and 80 XHTML components are supported, including list boxes, tree, drag-and-drop, auto-completion, sliders, timer, combo boxes, audio and many others. I found the user experience of ZK to be very fluid and can see it being a great resource for designers that do not have high-level programming skill, but still want to experiment with AJAX UI elements.
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focused on next generation websites.