Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Loxi - Easily add an events calendar to any website.
Event Hunt - Startups and Tech Events Curated By Locals
Event Calendar App - A simple, easy to manage, way of displaying events
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Whenever - Casual calendar app for iOS