There are many ways to save energy. Occupancy sensors that automatically turn on when a room is in use and turns itself off when it's not is a sure way to extend the life of lamps and lighting ballasts as well as reduce energy bills.
Timer switches like the one shown here are perfect for lights that are "out of sight and mind" like those used in attics, storage buildings, some closets, and similar spaces. Ever gone into an attic and pulled the chain only to find out that the bulb is burned out? Someone left it on after last use and energy was wasted for weeks or months until the bulb burned out. $$$$$