(by pio dal cin) I just moved my first steps into this new Google feature called Google Communities. It is rolling out slowly. As it is right now you can only join the groups that have been created but you are not allowed to create a group unless you received an invite from Google to become a moderator.
This video (excuse the poor quality but it was very late) shows you the first steps you need to take in order to enjoy the Communities which are just groups that you can join, according to your spèecific interests. So go on, into the left side bar, just under the "circle" icon and you'll see a green/white circle that says "NEW" in red. Click it ans start your experience on Google Communities