The International Energy Agency estimates between 3 and 13 percent of the costs on your electric bill comes from vampires.
Go here to check the kilowatt hour consumption of a particular appliance. The Lawrence Berkley National Laboratory, a U.S. Department of Energy lab operated by the University of California, created this searchable database.
The author suggests putting all such vampires (except for fridge and microwave) on electrical strips/surge protectors that can easily be turned off en masse by a flip of the switch, and he keeps his air conditioning thermostat set at 78 to 80 degrees, and he did an on-line home energy audit. This one is from OUC.