Alkarta - Find happenings in your city.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Soon - Never miss something awesome
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
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