1. Group Content Visibility
One of the great features in Organic Groups is the ability to create private content.
For example, say you have a bunch of training documentation that you want your new employees to go through. You want to put it on the web so they have access to it anywhere, but you don't really want to make it publicly available.
This can be done very easily with OG's Group Content Visibility setting.
Within the submission form of the content you wish to make private, just do the following:
Group Content Visibility field = Private - accessible only to group members
Click the Save button.