Try priceline.com. I just started using it and it truly does give you HUGE discounts on hotel rooms (>50%). The only thing about it though is that if they don't accept your offer, you have to wait 24 hours to offer again for the same trip. If you change the star level of the hotel you want you can offer again. Another thing is that if they accept your offer, you are charged and cannot cancel/get a refund.