If readers want to donate for nets, one good organization I have supported in the past is here. TamTam provides nets free at clinics. Personally I think this approach makes sense because charging dramatically reduces use, free distribution can help encourage mothers to come to antenatal clinics, and, like vaccines, insecticide treated nets can help interfere with disease transmission creating positive externalities. For some evidence on the first issue, see this paper.
One of the best buys out there is treating kids for worms. Two billion people have intestinal worms worldwide, including 400 million school-children. The medicine costs pennies per dose. Because the medicine is cheap and safe, but diagnosis is expensive, the World Health Organization recommends mass treatment in schools in areas of high prevalence, which can keep total costs per treated child to $0.25
Based on the evidence, several economists, including Esther Duflo, Kristin Forbes,and me, are involved in, and have donated to, a new group called Deworm the World. Information is available here. There is a donate button which explains how people can give.
Link to Mankiw Blog.