I'm officially an advocate for using Priceline's, "name your own price" bidding program for hotels and car rentals. This past year I've saved literally hundreds of dollars on hotel rooms by using the bidding method compared to booking directly with the hotel. For example, in Boston, I stayed at a Four Points by Sheraton property for $60/night, even though the hotel site was selling the same rooms for $129! In Washington D.C., I picked up a Marriott room for $58 bucks a night which was otherwise selling for $139 on the hotel site.
But using the "name your own price" function on Priceline isn't for everyone as it has a few risks. First, it's an Opaque site meaning that although you can select the neighborhood and star-rating of the hotel, you do not know the exact hotel name you are bidding for until after your bid is accepted. Some people don't like this uncertainty. Websites such as betterbidding.com offer forums where people can post winning Priceline bid information, which can assist you in knowing which hotels might be included in your bid request. Second, generally speaking you do not earn hotel stay credit or frequent flyer points when staying at these extremely discounted rates. Finally, you are fully pre-paying for your reservation which means no changes or refunds allowed.
Overall, if you are looking for a great deal on a hotel or car rental (they offer this for airline tickets too), and you feel adventurous, consider Priceline's, "name your own price."