Eduflow - Digital learning that actually teaches students something

Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.

Flowlingo - Get fluent in a language through content immersion

GroupSpaces - Free Group Website, Membership Database, Listserv Mailing List, Online Group Management Software : GroupSpaces

Backchannel Chat - Backchannel Chat is best in class discussion tool that is intended for teachers to streamline their class activities.

Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.