It's been freezing outside for a while now, and you may have heard it said that incandescent light bulbs help heat the house during the winter. That's not quite true. While incandescent light bulbs do use 90% of their watts creating heat, it's not heat that is useful or efficient. Heat rises, and since the vast majority of light bulbs are installed in the ceiling or at ceiling height, the heat has nowhere to go and dissipates before being useful to anyone.
If you were determined to utilize the heat produced by incandescent light bulbs, you could install them on the floor; otherwise, they're just not efficient sources of heat by any measure. If you need localized heating, standard space heaters would be the way to go, with energy efficient light bulbs for lighting. There are two main choices for energy efficient lighting; LED light bulbs, and compact fluorescent light bulbs.
LED light bulbs
are the newer of the two, and very expensive. They're completely safe, devoid of any toxic materials like mercury. Research and development into LED technology continues, and prices for LED light bulbs are dropping every year. Soon enough they will be affordable for everyone, and will be the best choice for energy efficient lighting.
The best most affordable energy efficient option right now would be compact fluorescent light bulbs
. They use around 75% less energy than incandescents, and have a wide variety of color temperatures available for really nice light. Their only caveat is the trace presence of mercury in each bulb; about 3mg in the newest CFLs, most of which adheres to the glass and does not spread if the bulb is broken. They're not a health hazard one at a time, but in the millions they would be hazardous, so they must be recycled.
Incandescent light bulbs are on the way out, and the myth that they can contribute useful heat during the winter is false.