Yes, you can bid on Priceline and you can buy at a set price on Hotwire. But here's the catch... you don't know what the hotel is until you have already paid (and it is non-refundable). Just a general location and star value. To me, one night would be worth it, a whole vaction, probably not.
There is a website about using these sites I think it is bidding for travel dot com.