I knew about couchsurfing.com for some time now. This site allows you to share your couch with a guest, or you could choose to sleep on someone's couch, air mattress or spare room for the night while you're exploring a particular city. This, of course, allows you to save significantly on travel costs. You can also opt to go to an event to meet couch surfers, and learn more about the whole concept. Has anyone couch surfed before?