I tend to spend quite a bit of time thinking about how some of the technical advances we have been making recently can be applied to improving quality of life for folks around the world. Hydroponics, aquaponics, cheap power generation, water distillation / filtration, atmospheric water extraction, housing, medical services, different applications for recycled materials, etc.
Recently I have been thinking alot about the various options for prefab and recycled housing and temporary shelters. There are quite a few interesting projects based on the Mongolian yurt (about $15-$90 USD per square foot), some interesting portable solutions for the homeless (about $500 USD per unit), and some interesting projects for permanent housing using shipping containers ($90-$150 USD per square foot) among others.
Now, the motivation for using shipping containers is multifaceted. For one thing, they are relatively cheap - used ones start at around $1200 USD and new ones can be bought for $6000 USD. They also have been piling up in US ports, as they are cheap enough that it is not worth shipping them back empty to countries that have an export imbalance with the US. Second, they are very solidly constructed for the transport of dense and heavy loads, and can hold up under a fairly wide variety of environmental conditions. Easy to transport to housing locations, of course, as they are designed for trucking applications. Sandblasting to remove existing coatings or residues is cheap and can be done by hand, and with a two layer coating of a ceramic paint, an R value of 28 is fairly easy to achieve. Further, they age fairly gracefully, and modular designs are easy and mostly a matter of stacking and cutting. Once stacked and cut, finish construction is relatively cheap and can often be done by the homeowner - run plumbing and electrical, install wallboard, floors, windows, doors, and fixtures.
Adam Kalkin is one architect who has been doing quite a bit of really interesting high end design and construction using prefab aircraft hangars and shipping containers. His Quik House project is an example of how to build cheaper high end housing, and runs approximately $184k USD for a 2000 square foot house using 6 shipping containers, coming in at around $92 USD per square foot.
It should be possible to reduce the costs for a shipping container based design by focusing on minimal amenities, smaller size, and functionality rather than focusing on the high end. A fully featured two container design (~700 square feet) could be finished for as little as $35k USD, or around $50 per square foot. Which is a pretty good figure for fully featured housing.
All of which implies that there ought to be an 'open source' housing project based around using used shipping containers as modular structural components. Various designs, suggestions for construction methods, coatings, fittings, and whatnot. Such an open source project could provide some housing options that are significantly more affordable than traditional construction methods and readily available to all.