Ruby-on-Rails (RoR) is a popular web-framework with plenty of successful web applications deployed. What made it unique when it came out is the concept of convention-over-configuration. RoR is very specific about where each bit of the web app goes and that allows developers starting to work in an existing project to find their way around it very quickly.
The use of convention-over-configuration might allow automatic transformation of RoR into similarly expressive frameworks such as Django or Symfony. The Python route looks the most promising given techniques to call Ruby code from Python, including some proof-of-concept bytecode translatators.