I think that straw bale houses are very interesting. I also read up on a San Diego company that makes a machine that makes large, interlocking bricks out of the soil at your homesite. You send them a sample of the dirt and they send you a recipe for mixing the dirt so that the brick is durable. They are very energy efficient houses that are also environmentally friendly.
As a side note, I think that all new homes in areas with a certain amount of sunlight (like AZ) should be required by law to have solar roof tiles (tiles, not the big ugly sheets).
