Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
GoodBarber - GoodBarber is a mobile app creation platform.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Siberian CMS - Siberian is an Open-Source and Free App Maker. Unlimited Push Notifications. Unlimited features. Fully Customizable. Download it and build your own app now!
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.
Dropsource - Mobile development platform for building native iOS & Android apps