Most Americans do not like to travel last minute. They need to plan their 2 weeks vacation very carefully. Often, one week is already tied up in time share!!
But, for expats / foreigners who are accustomed to travelling at the spur of the moment, or taking an impromptu trip (say, accross to the continent for the people who used to live in London) then I suggest getting onto www.gotoday.com.
It includes great deals from the US to anywhere. They are usually packages, and you may not use part of them, but they still seem to work out cheaper than if you buy the flights, hotels etc separately.
Just a suggestion....