Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
1up Events - Corporate events as a service
Event Hunt - Startups and Tech Events Curated By Locals
EventsApp - A simple concise app for creating and sharing events.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Rally by Eventbrite - Find the best local events and rally your friends to join