... reasonably priced thermostats available that could be used to switch a receptacle 'on' for use with a floor fan? The idea is to have the 'stat turn the fan on when the temp exceeds a certain setting and when the room cools down (when all are asleep) the 'stat shuts the fan off, thus saving sleep and energy.

http://www.smarthome.com/1625.html

Check that link out and see what you think. Sounds like exactly what you'd want. They want almost $60 for it, but search Ebay for the same product and you may luck out and get it for less.

Hope that helps!