Attendify - Develop relationships at the events that you attend by creating smaller events with just a few people.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
LineUpr - DIY mobile event app creation platform
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
Eventzilla - Eventzilla lets you sell tickets online and manage attendees from one integrated application.
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