DaySwitch claims to reduce lighting costs by 30% by using a simple concept: when it gets bright in the room, turn off the lights. Why people can't do this themselves, we don't know, but it might have something to do with getting up off their lazy asses every once in a while.
Researchers at Rensselaer Polytechnic Institute's Lighting Research Center who designed the light-sensitive switch say that it's so inexpensive, it could pay for itself in a year. There are already dimming systems available, but they're expensive and difficult to program and install.
Scientists Develop Simple Alternative for Harvesting Daylight and Saving Energy [Rensselaer Polytechnic Institute, via treehugger]