While most channels produce XHTML directly, you can use rich client technologies for channels.
Examples include Swing via Java Applets, AJAX (the architecture Google uses for things like GMail and Google Maps), the Flash-based Open Laszlo, and the JavaScript-based Qooxdoo.
Pete Boyson has implemented a theme called DnDPreferences that uses drag and drop for setting preferences in AL. It uses a JavaScript toolkit by Walter Zorn.
Direct Web Remoting is supposed to enable you to remote Spring managed beans to JavaScript.
Anyone producing channels using rich client technologies?
I collected a bunch of links on our own instance of confluence on rich client technologies...
User Interface Framework/Techniques
OpenLaszlo
Qoodoo
Tacos
Fade Anything Technique
AJAX XmlHttpRequest Links
Ajax XmlHttpRequest
Very Dynamic Web Interfaces using XmlHttpRequest
XmlgHttpRequest Object
XHConn - Simple XMLHTTP Interface
XmlHttpRequest demos
Ajax XmlHttpRequest working examples
AJAX XmlHttpRequest tutorial
Amazon Zuggest
Japano
Direct Web Remoting
Direct Web Remoting @java.net
DWR - Direct Web Remoting
JSON-RPC
DWR and Spring