Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Virtual Booth - A photo booth for virtual events
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
GetStream.io - APIs for the development of scalable newsfeeds and chat applications.
Bigtent - BigTent is a web-based organization and communication portal for groups.
Roomkey - Gamified social network for virtual events