Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Decision.io - Decision.io is an interesting platform that provides you the simple features to develop the app or an integrated workflow without using any program language or code.
Facebook Local - Discover places to go and events happening near you
RapidClipse - RapidClipse is a web-based development platform that allows you to build the app with Java and provides you with a hustle-free configuration.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Codeless Platforms - Codeless Platforms is a web-based platform that allows you to develop various applications and business processes without any coding and programming.