I released HTML::PopupTreeSelect::Dynamic yesterday, a dynamic AJAXified version of HTML::PopupTreeSelect. Instead of sending the entire tree to the client when the page loads, the new dynamic version renders the tree on-demand, retrieving nodes via AJAX requests. The result is a widget that can browse arbitrarily large trees without imposing long initial page-load times.
This was a learning experience for me - I'd never used the Prototype library before. Now I'm wishing I'd encountered it earlier - it would have made a number of Javascript-intensive projects much easier. I also got a chance to play with HTML::Prototype, which makes using the Prototype library from Perl a breeze.
All this learning will hopefully help me in the near future. I'm planning a much more involved DHTML/AJAX application as part of the continued development of Arcos at Plus Three.
-sam