Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Tinder - Tinder is how people meet. It's like real life, but better.
Event Hunt - Startups and Tech Events Curated By Locals
Pure - Spontaneous hangouts for singles
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Double - Tinder for double dates