FlexOnRails have two (first, second) detailed posts on using WebORB for Rails with Flex. The demo app uses Adobe’s Cairngorm a framework for Flex and it’s Value Objects which can be mapped (through WebORB) to server side objects. Make sure to read the comments on the second post as Derek Wischusen explains the value of Value Objects.
The app also makes use of a pretty cool reflection effect (which no Web 2.0 app can be without) by Ben Stucki (check out some of his other flex components).