Here's a wonky little chart that matters: Market-Based Strategies that Benefit Low-Income Communities. Laying out various challenges ("poor understanding of the human and social capitals of low income communities") and various approaches ("design products and services that tap into the wealth of poor"), it showcases nine solutions that seem to be working (such as, in this case, the solution of "acquiring technology through micro-leasing," illustrated by Fabio Rosa's program for distributing alternative energy systems to Brazil's rural poor).