Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.
Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
Bigtent - BigTent is a web-based organization and communication portal for groups.
Ticket Tribe - Sell tickets online with no fees per ticket
Nabble - Nabble is a forum software that are embeddable and fully customizable with scripting language.