Compact fluorescent CF bulbs -
The new CF bulbs are way diffewrent than the older ones, the light is a lot whiter. It take a few seconds to brighten up, but be patient. You can save up to $30 month on an average house. Those little savings add up, more if you're the landlord paying for the common area lighting that tenants always forget to turn off. (and if you have that problem, get a light timer, sometimes you have to take control and treat tenants like kids, cause some don't care.)