PHP Login framework to include google/facebook/openid etc
Not sure of any existing framework but this DB schema will satisfy all your expectations:
users
table - contains all user-related fields, except of authentication ones.
Plus 1 table per each authentication system:
auth_openid
with 2 fields openid_token | user_id
auth_facebook
with facebook_uid | user_id
etc
Found something called HybridAuth:http://hybridauth.sourceforge.net/index.html
Sounds good, going to give it a try.
Also found this, for python-django:http://uswaretech.com/blog/2009/08/django-socialauth-login-via-twitter-facebook-openid-yahoo-google/