Eventjoy - The Easiest Way To Organize An Event
Alkarta - Find happenings in your city.
Meetup for iOS and Android - Discover groups that are all about the things you love
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
TechEvents.co - Tech and startup events aggregator
Rally by Eventbrite - Find the best local events and rally your friends to join