XFN - The XHTML Friends Network 1.1 introduced the "me" rel value which is used for profile equivalency / identity-consolidation.
rel="me" is used on hyperlinks from one user profile of a person to other user profiles for that same person. E.g. on Tantek's Pownce profile it has:
<a href="http://twitter.com/t" rel="me">Twitter Profile</a>
You can use the XFN creator form to create rel-me hyperlinks.