Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Eduflow - Digital learning that actually teaches students something
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Flowlingo - Get fluent in a language through content immersion
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Padlet - Visual boards for organizing anything.