Airbnb is great. I've used it in Montreal, Denver, Lisbon, Rio de Janeiro and Barcelona. One tip to get an even greater deal on a listing you like is to send a message to the host saying that you'd like to negotiate on the price because you found a great place in great area of town for such and such price. If the host agrees, he or she will create a "special offer" listing that only you can see and that is cheaper than the publicly listed price. You can save yourself quite a few bucks doing this.