Gems/plugins used:

oauth - http://github.com/mojodna/oauth
authlogic - http://github.com/binarylogic/authlogic
facebooker - http://github.com/mmangino/facebooker
authlogic_oauth - http://github.com/jrallison/authlogic_oauth (Twitter)
authlogic_facebook_connect - http://github.com/kalasjocke/authlogic_facebook_connect

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TODO:

Connect regular registered acounts with twitter/fb
and cross connect fb registered accounts with twitter account (and vice versa)