In Rwanda, the MASS Design Group is using design principles to help improve health outcomes at a new hospital. The group's founder, a young architecture grad student named Michael Murphy, is working with Partners in Health and the Rwandan Ministry of Health to build the Butaro Hospital (north of Kigali). The hospital is designed to combat air-borne diseases by promoting more effective air circulation and by separating patients into dispersed hospital buildings. Other projects on the horizon for MASS Group include a school, an eco-tourism lodge, and a housing complex.
Here's another site with more information on projects connecting design with humanitarian needs. And here's another story from last year about a British NGO that is building housing in Rwanda with a focus on addressing some local housing challenges (dealing with flooding, insects, earthquakes) in an environmentally conscious manner and while using local materials. These houses end up being quite expensive by local standards but, as with all these projects, the key benefit may be to offer new ideas/new idioms for local builders.
(the photo of this typical Rwandan house was taken by my friend Puja Ahluwalia when we were in Rwanda together in 2008).