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

Raft Calendar - A fun and beautiful calendar for couples and close friends

Ticket19 - Sell tickets for your events with minimal transaction fees.

emble - Plan better events with your friends

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