Two real good ones...priceline.com and easyclicktravel.com
Easyclick is excellent in the Orlando area. Now, you won't know what you get until you book it, sort of. Here's how you defeat this, you look through the selections of hotels for your dates and it will come up with a list, star rating and prices. It will also state that (for the best deals) hotel name withheld until booked, but it does give a description of the property. Take that description and cut/paste it into google and you'll find out what hotel it actaully is. It works everytime. Easyclick must get the descritions off the hotels websites or something. I booked the Holiday Inn Resort for $51 for March 27th and on their Holiday Inn's webiste, it's listed as 140ish.
Priceline works in the same way but there's no way to know what you'll get for a star level. You can get close though if you use biddingfortravel.com and see what people are getting on priceline and you'll have an idea of what you should bid.