What should I use to create a login system for several sites similar to SO?

Question

I am creating a series of websites and web applications that will be hosted on a dedicated server that I own and accept. They will be developed on Windows Server 2008, IIS7 and .NET 4, SQL Server 2008 and Entity Framework. It will be a live server, and also a place for me to learn how to do some new things.

• User will have one username / password for all sites
• A user can have different access levels on each site.
• Login must be permanent in Remember Me sessions
• "Logout" registers the user from all sites.
• There will be some parts of sites on which anonymous is allowed.

I looked at OpenId and OAuth, and I'm not sure if any of them really fit the bill. I do not want to use something like Twitter for authentication, as I heard that it is filled with holes.

Answer 1

Here is a post that describes how they did it.

And in more detail.