Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
SurfersList - The ultimate online solution for finding, buying, and selling new and used surf equipment.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Fanatics - Fanatics is the leading online retailer of officially licensed sports merchandise!
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Wooter - Marketplace for sports & activities