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

Bigtent - BigTent is a web-based organization and communication portal for groups.