As communicated earlier, Yahoo! has opened doors to Open World and now you can integrate your Yahoo! accounts with your OpenID account.
Once you enable your Yahoo! account for OpenID access, you can simply tell any OpenID enabled web site that you are a Yahoo! user. You will be sent to Yahoo! to verify your Yahoo! ID and password and then signed in to the web site. Its that easy!
To access the service, go to Yahoo! OpenID (beta).