Consider replacing traditional thermostats with programmable ones.
According to ENERGY STAR, the average household spends $2,200 a year on energy bills and could save $180 a year by using a programmable thermostat to maintain proper heating and cooling settings. Seems like a no-brainer to spend a couple hundred dollars to save that same amount every year going forward, not to mention the unknown savings of having your systems run more efficiently.
One of my favorites is the new Nest Thermostat. From both design and simplicity standpoints, this seems like a great option. Check out how easy it is to program: