Automatically creating an organic group for each new user
The Rules module will allow you create new OG node after saving a new user account. Just do the following:


Create your rule and add an "After saving new user account" event to it
In the action section, select create a new entity
In the value section, select node
In the Content type, select the "your group"
Fill the title as you need; you can do this using the token
Fill the author


Hope this will help.