We may already informed about OpenID sign in process. Here we can understand how user can sign in to our websites with Google/Yahoo account via OpenID authorization process. Right Now OpenID is the best choice to sign in various websites with other website accounts.
Google and Yahoo also provide us OpenID authorization service that can help us to authenticate Google/Yahoo user from there site and call back to our sites with some user information along with unique identifier of the particular user. In this application we used a third-party OpenID class as this is very conceptual over the net.
[Google Authorization Demo] [Yahoo Authorization Demo]
Right now I am working on it and soon I will post source code here.