Mobilizon - A free and federated tool to get our events off Facebook
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
DownToMeet - DownToMeet is a platform to organize, find, and attend group events.
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
eventup - Find Great Event Venues in the US
Ticket Tribe - Sell tickets online with no fees per ticket