At the moment I am trying to get into the ASP.NET MVC framework. For most of my test applications I used a single assembly/project. This worked fine for some smaller app
I realize that this is a really old question but I have written an article on how to exactly what you are asking for
http://dotnetslackers.com/articles/aspnet/storing-asp-net-mvc-controllers-views-in-separate-assemblies.aspx