The Tumbleweed Tiny House Company sells minuscule prefab dwellings with themed appearances — New England manor, Gypsy caravan, artsy mid-century modern, etc. They're small enough to put up without a permit in most jurisdictions, but large enough to live (humbly) in them.
Update: Craig sez, "Thought I'd mention an article I wrote about Tumbleweed and some other tiny house companies that was published in the Chicago Tribune, Providence Journal, Arizona Republic, and some other papers. There's a woman who's building them as temporary homes for people whose houses were destroyed during Katrina."
Jeff sez, "looks like they sell plans, not houses; and make extravagant copyright demands:"
All of the designs are copyright of Tumbleweed Tiny House Company. A full set of plans must be purchased for each structure built. The construction of any design from Tumbleweed Tiny House Company without a purchased set of plans for that particular project is a violation of federal copyright law.