cheaptickets.com

You put the price you want to pay and see if the hotels will accept it.

If you want really cheap hotel rate, you will have to be out in the suburbs (just make sure the train, or T as they call it here, station is within walking distance from the hotel) and the hotel's star rating has to be low.

I once got a room at one of the decent hotels (Holiday Inn level) out in Burlington for around $35/night.

Hope this helps.