ASP.Net MVC.
Bootstrap.css, that ships with it, can handle much of the responsive needs.
EF on the backend
>If you were going to develop a new "responsive" web-site to handle mobile and browsers, what combination of packages would you use to do so? I'm coming from Silverlight, wpf, wcf, entity framework, etc.
Craig Berntson
MCSD, Microsoft .Net MVP, Grape City Community Influencer