Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
ParkingForMe - Marketplace for listing and renting unused parking spaces
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
On Air Parking - Ridiculously cheap and simple airport parking.
Bigtent - BigTent is a web-based organization and communication portal for groups.
Parking Kitty - New Product Hunt competitor for parking