Slack Events API - Subscribe to events in Slack via HTTP
1up Events - Corporate events as a service
B12 Bookings - Bookings scheduling software that integrates with your site
Calendify - Calendify is an event community where you can share, publish, and subscribe to event calendars. It helps you to stay informed about what you are interested in and what is yet to come.
Guestboard - Lead powerfully-organized group events with Guestboard – a modular event platform that gives groups of 10-1000+ people a central space to coordinate, build excitement, and save money. No more crazy email threads. No more massive group texts.
Facebook Local - Discover places to go and events happening near you