Travellar - A social travel app
Couchers.org - The new alternative to Couchsurfing. Non-profit. Community-focused. Well built.
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
Couchsurfing - CouchSurfing is your ticket to explore the world -- from the road or from your own home.
Magpie - Female travelers club - meet women like you when you travel
Hospitality Club - Free network of people around the world who offer free accommodation, advice and help when they are traveling - hospitality exchange. Free membership.