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

Ticket Tribe - Sell tickets online with no fees per ticket

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.

PromoTixApp - PromoTix is the world's first and only free online ticketing platform for events. Use PromoTix to create and ticket events, market events, and monetize your live stream event with secured and ticketed unique URLs online to the world.

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