Event Calendar App - A simple, easy to manage, way of displaying events
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Zoho Backstage - Plan, run, and analyze your event— all from one place
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
Meetabit - All the local tech and startup meetups in one place - easy to organize & attend