How do you rebuild a slum? You don't.
When churches and NGOs go in, will they rebuild the very structure that has sustained the dysfunction of Haitian government? The old model did not work from all I hear. Why rebuild it other than that is all we know. As the USA exploits the resources of its own country as well as others, sends the money for rebuilding the infrastructure and metro-dependent lifestyles, and infuses the same consumerism model we have here, there is a better way.
Many of the city people of Haiti are moving out to the country side where there is less desolation. That is where the solution resides. In the hills and valleys. A broad acre permaculture design for self sustaining agro-ecosystems could bring self reliance and empowerment to the Haitian people. The agrarian society that once was could be again the the citizens will live in a paradise of an edible forest jungle. From slavery to capitalist colonialism the island has been under siege for centuries and although the indigenous knowledge may be long gone, there culture has the land knowledge within them to rebuild a society based on locally supplied foods and sustainable agriculture.
Not economic development, not world bank or international loans, but small scale individual community support for agricultural restoration. Haiti could rebuild its soil, stop erosion and at the same time bring its culture from destitute to sustained independence. Resource independence through homestead subsistence farming that would develop into small scale agro-forestry is a better plan.
Tropical Permaculture Designers have those plans all ready to go. Better Life through Better Crops through Better Soil.