(new) For a summary, see Google's presentation given at the OpenID Retail Summit [March 2011]
Sample Sites
Blog post on Google's OpenID Sample Store - in particular we suggest watching the videos in the FAQ [Nov 2010]
Prototype of Google as an RP: federatedux.appspot.com [Summer 2010]
Google Account's use of OpenID & SAML as an RP in production
For email address validation - See blog post - Nov 2010
For SAML login - See training message for how to sign in to Google's regular login box. You will need a Google Apps account for a SAML enabled domain to test it [Summer 2010]
(new) Google looking for testers of using OpenID in production as an RP for login [March 2011]
Popular OpenID RP Services
Janrain, Ping, Azure ACS, Gigya
OpenID toolkits from Google
Raw OpenID RP feature in Google App Engine (see article) [July 2010]
(new) Google identity toolkit [March 2011]
The Google Accounts RP features described above are built on top of the same "raw" infrastructure as App Engine, but using a higher level toolkit
easyrpsample.appspot.com is a sample App Engine application using the same tools as Google Accounts
We will make those tools available (including the login box widget) as a service to any website who wants to copy Google's RP
Other vendor offerings will probably continue to be more sophisticated
If you are interested in these Google identity tools, contact esachs@google.com