Hi, its been ages since I came along and posted something in here..
Anyway, I've been playing a bit with Ruby on Rails recently and its pretty cool! I was mulling over something similar for the .NET platform and came across this:
http://www.codeplex.com/actionpack
It implements the "Rails" part in .NET. Sounds like it might be good fun. I doubt it will ever be as complete as Rails though because of the general awareness of Rails, but I thought i'd post about it here.