Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Foodie Advice - Get suggestions on what to eat during your travels
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Menu In Pictures - A crowdsourced map for restaurant menus
Bigtent - BigTent is a web-based organization and communication portal for groups.
Slaps - Social network for music