Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform
XCalSync - Automatically copy events between your calendars.
Zoho Backstage - Plan, run, and analyze your event— all from one place
Evounce - Easy and fast event planning platform
Meetup for iOS and Android - Discover groups that are all about the things you love
Eventjoy - The Easiest Way To Organize An Event