Jon Shumate introduces WebORB:

WebORB for Rails is server-side technology enabling connectivity between Flex and Flash Remoting clients and Ruby on Rails applications. WebORB for Rails can be installed as a plugin into any Rails application to expose Ruby classes as remote services. The product provides a complete implementation of the Adobe’s AMF0 and AMF3 messaging protocols and thus supports any Flash Remoting or Flex client.

Working with Flash and Flex? Check it out.