Campnab - Nab that sold-out campsite!
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Aerial Camping - Discover campgrounds from the sky ⛰
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Gamping - Airbnb for camping - Camping with a local
Bigtent - BigTent is a web-based organization and communication portal for groups.