Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
GraphJS - Make any website social
Cvent - Cvent's event management software provides event planners with a complete solution to increase event attendance and decrease event costs.
MyTalk - Build a community around your product
Ticket Tailor - Ticket Tailor is an easy-to-use event ticketing platform that allows event organizers of all shapes and sizes to sell tickets online.