If you want to get fancy, X-10 makes a device that sits under your
thermostat and produces a bit of heat, so it fools the thermostat into
a lower setting.

If you also get a telephone responder you should be able to call your
house and turn that device off before returning home, with enough
advanced notice to let it warm back up. This would have the added
advantage of letting the house stay colder longer if you end up out
longer than you originally planned.

With the disadvantage that you may occasionally forget to call, and
then you'll come home to a cold house.

Shaun Eli
www.BrainChampagne.com
Brain Champagne: Clever Comedy for Smart Minds (sm)