Alkarta - Find happenings in your city.
TechEvents.co - Tech and startup events aggregator
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
Facebook Local - Discover places to go and events happening near you
Rally by Eventbrite - Find the best local events and rally your friends to join
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets