You will not save money even if you use CFLs, when lights are left on for no reason.  With our recent remodel, we installed several light switches that automatically turn off. These are required by California’s Title 22 code.

Vacancy sensors detect when a space becomes vacant and turn lighting off automatically after a preset time delay elapses.  They also make other specialized versions that have fixed 5 minutes delays, good for closets.

These switches replace standard light switches, so they can be easily retrofitted.  Most cost under $50.