Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Detour - Immersive audio walks, now in 17 cities
Facebook Local - Discover places to go and events happening near you
Sygic Travel Maps - Itinerary planner for independent travelers
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Flamyngo - Create a city guide with help of your friends.