javascript webdev
(Mister Wong community recommendations)
most popular brand new
node.js
Very tempting. Server-side JavaScript, designed around event-based programming rather than straight declarative flow, which means it's a whole heck of a lot easier to write long-polling style AJAX ...Sanjiv Jivan's Blog
Databound widgets, comprehensive set, that tie into GWT cleanly. Not lightweight, but who the hell cares when it gets the job done so well?