This is turning out to be quite a good week for OpenID, an increasingly popular mechanism for creating and managing a single identity across the Internet. On Monday, Microsoft announced that it would give every Windows Live user an OpenID account, and today, Google announced a very similar plan.

Google will allow web services to join a limited test of an API based on the OpenID 2.0 protocol that will give Google Account users the option to sign in to websites with their Google credentials and without having to sign up for a new account at those sites.

Among the launch partners for this new API are Zoho, Plaxo, and Buxfer.

Don't Mention OpenID

One of the key results of Yahoo's OpenID usability study was that users did not understand OpenID and what its logo stands for. Instead, Yahoo promoted the idea of giving users a sign-in button that simply said "Sign In with a Yahoo! ID" (though Chris Messina argues that this could be detrimental to OpenID in the long run).Google and its partners are taking a similar route and are basically bypassing any mention of OpenID itself in favor of a simple message saying "Sign in with a Google Account."

More to Come

Google also announced that it is looking to combine the OAuth and OpenID protocol so that a service can not only request a user's identity through OpenID, but also "request access to information available via OAuth-enabled APIs such as Google Data APIs as well as standard data formats such as Portable Contacts and OpenSocial REST APIs."

Tipping Point?

Thanks to this announcement, a wide range of some of the web's largest service providers now supports OpenID: Yahoo, Google, Microsoft, MySpace, and AOL.

As John McCrea notes, the result of these announcements from Google and Microsoft this week should be "a massive adoption wave for OpenID all over the web."