>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.

asp.net MVC +1
Bootstrap.css +1

EF is the big ORM, but also consider a micro-ORM like Dapper