RentHoop - Tinder for finding roommates
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
Splitwise - Splitwise is a free tool for friends and roommates to track bills and other shared expenses, so that everyone gets paid back. On the web, iPhone, and Android!
Palaround - Meet people you should be friends with.
Pack - Makes it simple to find the best roommates.
Babble - A more personalized social network