If you don't look at anything else, check out Home Energy.
James Dulley has a regular newspaper column on household energy savings, and this site too.
Do you want to get really serious? Check out Home Power, which shows you how you can generate your own power and get off the grid. Unfortunately they let political nonsense detract from their message somewhat.
Kansas Windpower has been around for a while and I've heard good things about them. And there's Sunelco in Montana.
For a more yuppified approach there's Real Goods Trading from Ukiah, CA. They have a demonstration project described here.
Here are directories for solar photovoltaic (PV) and wind power related businesses.
Then there's straw bale construction, earth sheltered construction, passive solar...I'd dig up more if I had the energy.