This weekend, I bought the first of what I hope is many LED light bulbs for my house.
It's got the standard screw fitting, no mercury (unlike CFL), lasts a long time, and uses 1.5 Watts of power to have equivalent light output to a 40 Watts incandescent bulb. It also runs cooler.
Downsides are the $9.99 price, and incompatibility with dimmers.
I look forward to developments in this area.
Statistics I found were that 8.8% of household electricity consumption in the US is for lighting. Decreasing that by 95% will make a big dent in overall electricity consumption.