Sources of Identity Information

Facebook Connect

OpenID

Twitter

Google Friend Connect

Google

Google Apps

Yahoo

Open Social

LinkedIn (45 million users)

Plaxo

Xing (8 million users)

Ning (1.5 million networks, 33 million registrants)

myspace

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Systems that support these:

Ning (NingID, Open Social)

http://www.readwriteweb.com/archives/ning_launches_ning_apps.php

Zoho (Google, Google Apps, Yahoo)