Check insulation levels in the attic and walls.
For northern climates, do you have at least 18 inches of insulation in the attic and is the attic entry area insulated? Make sure the foundation or basement wall also is insulated at least 4 feet below the ground surface to at least an R-10. You wouldn't want your walls to be un-insulated. Why would you let your foundation go without insulation? Heat is lost to cold and frozen soil.

Install insulating window treatments.
The R-value (insulating ability) of windows is low even with triple glazing. By properly installing quilted drapes or blinds, you can increase the insulation value of these areas significantly. Room air must be restricted from reaching the window to achieve maximum insulating value.

When replacing appliances, look for the ENERGY STAR label.
The initial cost of these appliances will be higher, but those costs will be recovered due to lower operating costs. Front-loading washing machines save energy costs both for washing and drying. They use smaller amounts of water and, since they have high-speed spin cycles, they also reduce energy spent on drying.

Install an ENERGY STAR programmable thermostat.
With a programmable thermostat, you can achieve thermostat setbacks with little effort on your part. The thermostat can turn down automatically when you go to bed and be programmed to turn on before you get up in the morning.

Plant trees.
A longer-term project is to plant deciduous trees on the south side of your house. The trees provide shade in the summer, lowering cooling costs, and when they lose their leaves in winter, they allow the sun to heat your house naturally. Plant evergreens on the north side to help block winter winds.