Google Identity Toolkit (GITkit) helps relying party (RP) websites to support federated login easily (http://code.google.com/apis/identitytoolkit).

Hassle free implementation of Social share buttons, social content locker & social like using just one plugin. Best social share plugin to increase social traffic

Social Login by Janrain

Provides a simple and very lite social login system for your Wordpress without any server overloads !