ASP.NET SAML - ASP.NET SAML is an open-source authentication utility that has been used for exchanging authentication and authorization data between the channels.
Notopass - Share your accounts without giving username/password
DotNetOpenAuth - DotNetOpenAuth is a free-to-use compiled library that comes with the real support to your site visitor to login with the help of openIDs via getting control of the ASP.NET control onto the page.
1Password - 1Password can create strong, unique passwords for you, remember them, and restore them, all directly in your web browser.
ASP.NET Identity - ASP.NET Identity is a membership-based software system designed for the authentication and authorization of the users via building an ASP.NET application.
ShareAccount - Share your account without giving out your password