I\'m looking learn about ASP.NET MVC and OpenId using the ASP.NET MVC NerdDinner tutorial.
I would like to replace the Authentication system in NerdDinner to be Open
Look at the Samples/OpenIdRelyingPartyMvc dir (a simple ASP.NET MVC website using OpenId authentication). You can start from copying Home/User Controllers/Views and settings from web.config into your project. I think it is the fastest way to give your site OpenId authentication. Then, as Alexander Prokofyev said, there is very useful post at the Andrew Arnott's (DotNetOpenAuth/DotNetOpenId author) blog - Add OpenID login support to your ASP.NET MVC site