Any successful idea, such as renting out rooms or apartments on a short-term basis to travellers, usually sparks competition. While Airbnb (www.airbnb.com) is the largest room-sharing service, it does have competition.
One of them is called Wimdu (www.wimdu.com) and some of its offerings are bargain-priced, such as a room in the heart of Havana for just $29 a night, a one-bedroom apartment in Berlin for $74, a room along the Seine 15 minutes from Paris for $55, or an apartment with balcony in Split, Croatia for just $44.
Another company in the same business is Roomorama (www.roomorama.com.) Its lodgings seem to be higher-priced, though that may mainly reflect market rates. For example, in London a small (322 sq.ft.) studio apartment near Broadway market will set you back $205 per night, and a number of other places for rent are still more costly. In Berlin, a one-bedroom apartment with balcony in the central Mitte neighbourhood goes for $155 per night.
With all these services, you need to do your homework. Read reviews if available, check the policies on cancellations and so forth. You will be dealing with a private person in most cases, and it is not like a hotel where there is more structure and often a connection to a hotel chain in case you have serious problems. There have been some horror stories about using these roomsharing services, but then it is also possible to have hassles with hotels. As always, the rule is caveat emptor.