Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Huntathon - Browse and submit Product Hunt Global Hackathon projects
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
CoFoundersLab - Meet 250,000+ entrepreneurs 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
Confs.tech - Open source list of tech conferences: JS / Ruby / Data etc.