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

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

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

Calendify - Calendify is an event community where you can share, publish, and subscribe to event calendars. It helps you to stay informed about what you are interested in and what is yet to come.

Ticket Tribe - Sell tickets online with no fees per ticket