Thijs Feryn writes an excellent article on how to convert your entire MVC app or one or more controllers into a XML service. I actually have this one in a production environment and it works like a charm.
That’s right folks, in this blog post I’ll show you how you can convert your entire MVC application into a REST-style XML webservice. And I’m not talking about refactoring tons of code … NO, we’ll plug this option in without changing a single thing to your action controllers.

