Objective Resource is an easy-to-deploy framework that allows an iPhone app to be easily synchronized with data from a Ruby on Rails application.  It allows developers to serialize objects and pass them to or retrieve them from a Ruby on Rails app with simple one-line commands from the Objective Resource Objective-C library.  Check out their 6-minute screen cast to see what Objective Resource can do for your app.

http://iphoneonrails.com/