Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
It's On Meet - Unlock who you want to meet by accepting a drink or not
Facebook Local - Discover places to go and events happening near you
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
FriendsTonight - Meet new friends to join your friends, tonight