Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
TechEvents.co - Tech and startup events aggregator
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
Facebook Local - Discover places to go and events happening near you
Ticket Tribe - Sell tickets online with no fees per ticket