Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.

Openki - Platform where you can search, propose, take part, help organize or publish workshops, lectures...

Eventbrite - Discover Great Events or Create Your Own & Sell Tickets

Citybound - Open-source city building sim with a focus on realism through microscopic details

Bigtent - BigTent is a web-based organization and communication portal for groups.

SimCity BuildIt - Build, craft, and control! SimCity BuildIt is an all-new SimCity game designed just for mobile.