Here is a combo platter of a whole lot of TreeHugger favorite things, found on Tiny House Talk: The FOUNDHOUSE.
First there was the Wikihouse, "an Open Community Construction Set. Its aim is to make it possible for almost anyone, regardless of their formal skills, to freely download and build structures which are affordable and suited to their needs."
Then there is DesignBuildBLUFF, the wonderful student design/build project from the University of Colorado where "Calloused hands, engaged minds, and open hearts align with resourcefulness and ingenuity to create a home for some of the last people to expect it."
Now there is FOUNDhouse, where Patrick and Lacey use the Wikihouse technology to build a tiny house to house students working on the DesignbuildBLUFF project.
The wikihouse system uses a CNC router to cut out complicated plywood shapes that snap together quickly and easily without the need for nails. The designers then can finish the inside and outside with whatever they want; in this case they have clad it in siding made from pallets, yet another staple of TreeHugger.
A benefit of the snap-together nature of the structure is that they could assemble it in Denver, take it apart and reassemble it in Utah. Otherwise I wonder how much more efficient it really is than using conventional wood framing; there is a lot of complicated cutting out of the sheet of plywood and a fair amount of waste material here. It doesn't seem to me to have the advantages of the FACIT system, where the product is a "cassette", or a box that is at once the frame, sheathing, interior wall and is designed to hold insulation.
However it does go together quickly. Wikihouse is a completely open system, certified under Creative Commons, so anyone can go on the site and download plans, modify them is Sketchup as required, and send them off to the local CNC router. So anyone who wants this particular tiny house plan can have it, and anyone who has ever played with lego can probably build it.
And they do pack a lot into 150 square feet. More photos at FoundHouse.