Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.

Get Together - Get Together is an open source event manager for local communities.

Eventbrite - Discover Great Events or Create Your Own & Sell Tickets

Calendify - Calendify is an event community where you can share, publish, and subscribe to event calendars. It helps you to stay informed about what you are interested in and what is yet to come.

Guestboard - Lead powerfully-organized group events with Guestboard – a modular event platform that gives groups of 10-1000+ people a central space to coordinate, build excitement, and save money. No more crazy email threads. No more massive group texts.

Meetabit - All the local tech and startup meetups in one place - easy to organize & attend