I realize this question is a bit subjective but it seems like best practices are still evolving for ASP.Net MVC.
I went searching for examples on how to implement sub/partial views with their own controllers so that I could produce self contained widgets and I came across this article.
http://blog.codeville.net/2008/10/14/partial-requests-in-aspnet-mvc/
It works but I'm curious if anyone with a bit more experience with this kind of thing can see some roadblocks I may run into with this approach.