A while back I used Betterbidding.com to help me make the best bid on Priceline Hotels and ended up getting about $99 $75 a night for a Club Quarters room in Chicago when the conference rate at the nearby (four blocks away) Palmer House Hilton was over $160 $169 a night. I saved $282.
The users and especially the site manager there will bend over backwards to help you find the best rate, even going so far as to post a detailed multi-step bidding strategy to take advantage of some quirks of Priceline bidding. Basically, a rejected bid is not the end.
Here's a link to the discussion thread on the forum for the Chicago trip, which includes the bidding strategy they posted for me.