Thinking again about back to school - turn off your computer at night to save energy.  Turning off your computer instead of leaving it in "sleep mode", can save 40 watt-hours per day.  This can really add up - first, it decreases the amount of carbon dioxide emissions released into the atmosphere (and contributing to global warming), but it can also save money on your electricity bill.  Up to $14 a year.  So power off at night and on weekends!