Try setting your thermostat to 78 degrees and using your ceiling fans to circulate the air.  You use approximately 3% less energy for each 1 degree increase on your thermostat during the summer.

Better Yet:

If you have a programmable thermostat, consider setting it at 80 degrees when no one is home.  Cooling your house just before you get home uses a lot less electricity and costs a lot less than keeping it cool all of the time.

For More Information

The US Department of Energy has much more information on how to get the most out of your household appliances for the minimum cost: