Zed Shaw put together a simple proof of concept application in a couple of hours to demonstrate the possibilities for rich clients in Rails and XUL. Being XUL, it naturally only works in Firefox and Mozilla, and being proof of concept, it still has plenty of stuff missing. But it does provide a window into the kind of applications Rails are capable of powering if you’re willing to limit the application to the Mozilla platform.

UPDATE: Zed has explained how the prototype works and offers a few suggestions for Rails.