Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Cvent - Cvent's event management software provides event planners with a complete solution to increase event attendance and decrease event costs.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
EventMobi - EventMobi is an interactive mobile event app, audience response and engagement platform for conferences and trade shows.
Bylde - Bylde is a SaaS platform you can use to Start, Manage and Grow your groups and communities.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.