Which one do you guys use to book hotel rooms? I usually use Travelocity, but Orbitz has more choices available. The prices are always the same on all of them. Hotel.com is another. Am I missing anything else?
If you know for certain the time period you want to stay, I'd say screw them all and go with priceline.com or hotwire. I've gotten $125/night rooms for around $38/night in California and similar in San Antonio. You can't get your money back if you decide to change dates or cancel altogether, though. If interested, check out www.biddingfortravel.com.
From what I understand, companies like Expedia and Orbitz are joint ventures of the major airlines. And for hotels, contact hotels directly. There are times that I find a cheaper price on promotions from the hotels themselves than from hotels.com or whatever. Here is a link that might help, even if it is a bit dated: http://www.forbes.com/2003/08/21/cx_cv_0821feat.html
You should just check them all.... and then check if there is a flight/hotel/car package you can get which will save you a ton of money. Check priceline, too... but only after seeing the probable price on hotwire. Take the hotwire price, subtract 20%, and that's a good rule of thumb for what you should bid. On a related note, check http://www.biddingfortravel.com for recent winning bids. And finally, the advice about checking with the hotels directly is correct. A lot of hotels in the past two years (I think one of the major chains, too) do not use the online services anymore. You should both check the individual websites AND call them for the best rate. Oh, and if you want tips on upcoming deals, check MSNBC's travel section (and travel blog web page), which lists deals as they find out about them. I used this info to get a trip to Spain for $200 less than advertised everywhere else. If you want a list of the sites I usually check, give me a call.