B12 Bookings - Bookings scheduling software that integrates with your site
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Eventjoy - The Easiest Way To Organize An Event
Event Hunt - Startups and Tech Events Curated By Locals
Klook - Discover & book amazing experiences at exclusive prices
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets