Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Verlocal iOS App - The app to rediscover your city with local experiences.
Event Hunt - Startups and Tech Events Curated By Locals
Flamyngo - Create a city guide with help of your friends.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.