Here is a lecture in two parts of Alejandro Aravena about their partial self build social housing.
The genius idea is essentially to build half of the house so that the inhabitant can self build the other half. This allows houses which are twice bigger than they would be otherwise. At the same time, it enables the inhabitants to be in control and responsible for their future.
As the recording doesn't show the images, it is worth looking at their website at the same time.