Using painted galvanized steel structural insulated foam panels (SIPs), my awesome brother (the one wearing the hat) put together my 96 square meter (including the large verandah) house in 4 weekends. That's 1033 square feet. The building materials are all readily available and cheap, with the big expense being the concrete foundation that's needed to bolt the panels to.
The panels are highly insulated and make for comfortable temperatures inside year round, saving up to 50% on energy costs compared to other building styles. I also chose a cool and breezy mountain-foot site to build. I have 3 solar photovoltaic panels and 2 wind generators for power, connected to a sinewave inverter.
I was initially going to make a much smaller house, but quickly realised that the panels were so cheap that adding another room and a large verandah wouldn't increase the cost much at all. If I need more space in the future, I can close the verandah and turn it into another room.
Because we didn't use a skeleton frame, the house has to be a bungalow. For multi-storey buildings, a steel skeleton frame is needed.
More information about SIPs here: http://www.eco-panels.com/
(I didn't use this US company as I'm European, but their website is informative)