What is the equivalent to Page.ResolveUrl in ASP.NET MVC?

This should do what you're looking for...

System.Web.VirtualPathUtility.ToAbsolute("~/")

It is Url.Content:

ASPX:

<link rel="stylesheet" href="<%= Url.Content("~/Content/style.css") %>" type="text/css" />

Razor:

<link rel="stylesheet" href="@Url.Content("~/Content/style.css")" type="text/css" />