Google + Communities

The communities for an educator to join on Google + seem endless!  Here are just a few I found to join that look cool:  
National Geographic Education
https://plus.google.com/u/0/communities/105645984815440438942
Educators on Google +
https://plus.google.com/u/0/communities/100342834366095345013
and
Science for Kids
https://plus.google.com/u/0/communities/110227751651106614300