Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Hive - Seamless project management and collaboration for your team.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Sup! Standup Bot - The complete stand-up and follow-up bot
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.