Google is now offering an OpenID service:
Google supports the OpenID 2.0 Directed Identity protocol, and provides authentication support as an OpenID provider. Google authenticates the users signing into their existing Google account, and returns to the third-party application a consistent identifier that the application can use to recognize the user. Google also supports OpenID Attribute Exchange 1.0, which enables Google to share, with the user’s approval, the primary email address associated with the user’s Google account.
Microsoft announced to turning their Windows Live ID offering to being an OpenID provider by publishing a Community Technology Preview (CTP) of the so called “Windows Live ID OpenID Provider”.
The Windows Live ID OpenID Provider (OP) enables anyone with a Windows Live ID account to set up an OpenID alias and to use that alias for identification at an increasing number of OpenID 2.0 relying party sites
Both are one way OpenID implementations meaning you can not leverage your own existing OpenID to authenticate to any of the Google or Microsoft services which actually is the whole point, like also stated at openid.net:
You get to choose the OpenID Provider that best meets your needs and most importantly that you trust. At the same time, your OpenID can stay with you, no matter which Provider you move to. And best of all, the OpenID technology is not proprietary and is completely free.
