“We’re releasing full OpenID relying-party support, so you’ll be able to sign up for a Plaxo account using an OpenID and/or attach OpenIDs to your existing Plaxo account. I’m also publishing a step-by-step implementation guide for OpenID-enabling existing sites based on the work I did for Plaxo.”
He has put up a whole set of shots on Flickr outlining the steps.
This is another great step for OpenID!!!!
They are also publishing an implementation guide for relying parties.