I came across this when trying to build a website that takes advantage of sub domains in a MVC project. You can route subdomains in MVC to a particular controller, and specific actions.

In order to do this, you must make your website listen directly on the IP Address, and point a wildcard A record for all subdomains. In IIS 7, under Bindings, add a binding for http or https, set the IP to the dedicated IP for the site, and leave the Host name empty.

In your DNS Server (GoDaddy or Windows DNS Server), add the following A records

Host: @ or (same as parent)
IP address: (your dedicated IP)
Host: *
IP address: (your dedicated IP)
NOTE: Not all DNS Servers have wildcard options

This will make your website listen for any subdomains on your site.

Reference the classes attached below, and add the following routes to your project

_routes.Add("BlogRouteProfile", new DomainRoute("{url}.example.com", "", new { controller = "Blog", action = "ViewBlog", url = "" }));
_routes.Add("BlogLatestPosts", new DomainRoute("{url}.example.com", "latest-posts", new { controller = "Blog", action = "BlogLatestPosts", url = "" }));
_routes.Add("BlogPost1", new DomainRoute("{url}.example.com", "rss", new { controller = "Blog", action = "BlogRss", url = "" }));
_routes.Add("BlogPost3", new DomainRoute("{url}.example.com", "pages/{pageName}", new { controller = "Blog", action = "BlogPageView", url = "" }));

In your controller, you can now define Actions, just as you normally would for a regular route.

public class BlogController : Controller
{
    public ActionResult BlogPageView(string url, string pageName)
    {
        return View();
    }
}