Mobilizon - A free and federated tool to get our events off Facebook
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Wooter - Marketplace for sports & activities
DownToMeet - DownToMeet is a platform to organize, find, and attend group events.
SurfersList - The ultimate online solution for finding, buying, and selling new and used surf equipment.
Get Together - Get Together is an open source event manager for local communities.