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.
Event Hunt - Startups and Tech Events Curated By Locals
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!
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Dropsource - Mobile development platform for building native iOS & Android apps