Yahoo OpenId Support Launching on Jan 30. Through this facility a Yahoo user will be able to use that login information to access non-Yahoo Web sites that support the OpenID 2.0 Digital Identity Framework.
OpenID 2.0 will help in reducing the amount of different log-in information people need to create, remember and enter inline.
At present more than "Ten Thousand" Web sites support OpenID 2.0

Yahoo's move will triple the number of OpenID accounts to 368 million by adding its 248 million active registered users to the rolls, the company said Thursday.

Yahoo.com