Airbnb - Book unique places to stay and things to do.
BeWelcome - Open your door to the world!
Travel to Live - Live to travel. Travel to Live!
Trustroots - Travellers community for sharing, hosting and getting people together.
TripIt - TripIt is a travel app that creates a master itinerary to organize all of your plans for your vacation or work trip in one spot.
Hospitality Club - Free network of people around the world who offer free accommodation, advice and help when they are traveling - hospitality exchange. Free membership.