Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Skyscanner - Skyscanner.com compares over 1000 airlines to find you the cheapest airfares, fast.
Event Hunt - Startups and Tech Events Curated By Locals
Kiwi.com - Find and book the best low-cost flights all around the world
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
App in the Air - The perfect companion for everyone taking a flight.