The "$50 Underground House":
My interest in this is partially inspired by the tumbleweed/tiny house idea, but combining it with a survivalist edge--who doesn't want a house that doubles as a bomb shelter? I'm picturing a regular brick shed (since I need one of these in my yard anyway and it provides camouflage) with a hidden trap door hatch to a fallout shelter/living space beneath. The difficult part would seem to be plumbing and, to a lesser extent, electricity. Other than that it seems like just digging a hole, more or less.
These designs look a lot more complex than that, with windows and everything--basically a Hobbit House, lol--but I could do without that, or perhaps design it so the upper level of the shed is habitable as well.
I could build this in my back yard, live in it while renting out my actual house for its full value, and ERE in 5 years!
I'll look for the "$50 Underground House" book at the library.
On a semi-related note, check out this freaky youtube video from the 1950's "Fallout: When And How To Protect Yourself Against It" (http://www.youtube.com/watch?v=G8_q06SL98Q)