My buddy Dan Hoffer started CouchSurfing.com, an incredible Internet service that let's you meet total strangers and either host them on your couch, or stay on theirs. I joined the site and haven't gotten enough nerve to host someone yet, but I'm sure I will this month. CouchSurfing was written up in the Wall Street Journal and I loved the quote from the article written by Anne Kadet below.
"Everyone has their own reasons for hosting strangers. Site spokesman Cesar Valentim says that for people in places such as Nepal, where international travel is financially or bureaucratically impossible, hosting provides an at-home adventure. For New Yorkers, he says, hosting offers a social life to folks who otherwise "don't have time to go out and meet new people." Ouch!
I can think of a third reason to host: Welcoming travelers to your NYC apartment—who can then testify on your profile that you are neither a psychopath nor an open-mouth chewer—is the best way to improve your odds of finding a couch when it's your turn to travel. And couchsurfing lets you stay in places where it's impossible to find a hotel room—like an Amazonian village or an Antarctic field station."