Self-taught builder Simon Dale constructed this straight-out-of-a-fantasy-novel house in four months for less than $5,000. The house is designed for low-impact building and low-impact living: it was made from reclaimed lumber and salvaged materials, and the Dales live off the grid, with a compost toilet, a green roof, spring-sourced water, and natural heating and cooling. Plus, have we mentioned that it's unrealistically beautiful? It looks like they should have a one-unicorn garage.
If you're interested in a similar project, Dale has posted plans, process photos, and thoughts about the how and why of his hobbit hole on his website.