Topic: Using third party api's to manage user authentication

Hey, I am learning Ruby on Rails and reached a stage where I am learning how to create User Models, User databases and managing/administrating users.
Whilst I am learning how to create these from scratch, I am interested in getting peoples views and experiences using Google and LinkedIn's api's to manage users and content.

if using these types of api's how do you administer users, content etc?

Cheers,
Mark.