One of GiveWell's top charities for the past several years, AMF provides anti-malarial bednets to people in need. 

From Givewell: 
What do they do? AMF (againstmalaria.com) provides funding for long-lasting insecticide-treated net (LLIN) distributions (for protection against malaria) in developing countries. (More)

Does it work? There is strong evidence that distributing LLINs reduces child mortality and malaria cases. AMF conducts post-distribution surveys of completed distributions to determine whether LLINs have reached their intended destinations and how long they remain in good condition. AMF's post-distribution surveys have generally found positive results but have some methodological limitations. (More)

What do you get for your dollar? We estimate that the cost to purchase and distribute an AMF-funded net is $4.95, or $4.65 excluding in-kind contributions from governments. The numbers of deaths averted and other benefits of distributing LLINs are a function of a number of difficult-to-estimate factors, which we discuss in detail below. (More)

Is there room for more funding? We believe that AMF is likely to be constrained by funding. We estimate that AMF could use up to an additional $37.8 million to support LLIN distributions that will occur between now and late 2023. 

AMF is recommended because of its:

Focus on a program with excellent evidence of effectiveness and cost-effectiveness.
Processes for ensuring that nets reach their intended recipients and monitoring whether they remain in homes and in good condition over the long-term.
Room for more funding – we believe AMF will be able to use additional funds to deliver additional nets.
Transparency – AMF shares significant information about its work with us and we are able to closely follow and understand its work.