Eventcal - Facebook events filtered for your calendar
Mobilizon - A free and federated tool to get our events off Facebook
Facebook Local - Discover places to go and events happening near you
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
DownToMeet - DownToMeet is a platform to organize, find, and attend group events.