Eventbrite - Discover Great Events or Create Your Own & Sell Tickets

Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.

Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform

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.

pretix - pretix helps you to sell tickets for your event in an easy way. It supports multi-lingual events and provides a wide range of features

SkillMint - Find, meet and rate people with common skills and interests. Community-driven rating system.