Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Evendo - Events. Efficient. Easy.
Ticket Tailor - Ticket Tailor is an easy-to-use event ticketing platform that allows event organizers of all shapes and sizes to sell tickets online.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
YurPlan - Event administrator - Event Agenda - Ticketing Service - A new way of experiencing an event