I'm doing research and development to start a new project using J2EE and Ajax technologies. Have looked at a few architectures ( DWR,Prototype, Rico, Echo2 etc ). Pretty impressed by the way Zimbara's architecture. I haven't checked out the code yet, but will do soon and see if I can add hooks in Zimbara to talk to most of the action based architectures, if it works out , will definately try and make it as a plugin and post it here.