Winkli - Discover who you'll bump into at your Facebook events
Event Finda - Find events near you, and all around the world.
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
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
Humbler - Find events that support causes you care about