Journy - Tastemaker-driven concierge to plan your perfect trip
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Sygic Travel Maps - Itinerary planner for independent travelers
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
The Basetrip - Cities - Travel information for 650+ cities & 230+ countries
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets