I just saw a program on Straw Bale building today. It really amazing and made me want to build one! You could tell how much the straw bales absorbed the sound and they only spend $2600 on straw to build all the outside walls in the house (a very large house). They did steel beams to frame in the house and then they also used a recycled blue jean insulation in all the interior walls and in the roof.
That sounds very interesting and cost efficient. saw a show a few weeks ago about a man who built a home with some type of military bags for insulaton. He used thousands of them and then used some sort of stucco material to cover it up inside and out. His electric bill is only 25.00 a month!!