Check out this neat company, Tumbleweed Tiny House Company, that I found while reading a new fave site, RiverWired. (an awesome "green" social network site full of relevant and interesting news and stories)
Tumbleweed Houses are incredibly small and built for people that can really appreciate living in a small small space. They are eco-friendly structures and smartly built.
(picture top : bottom)
Biensi House (70 sq ft)
Weebee House (110 sq ft)