The first issue of PLoS Medicine, published by the Public Library of Science, came out about five years 
ago. Its aim at the time was to provide an open-access alternative to top-tier subscription medical journals such as the New England Journal of Medicine and The Lancet. They have also tried to distinguish PLoS Medicine from other journals in several ways. In this regard, one distinguishing feature of PLoS Medicine is a ban on advertisements for drugs or medical devices.
Another stated aim was to be a journal that had a clear priority of publishing papers on diseases that take the greatest toll on health globally. The editiorial in the latest issue reaffirms and adds to this by stating PLoS Medicine "will take an evidence-based approach to identifying topics of global health priority, and will give highest priority to publishing studies that advance human health in these areas."
Take a read!
The latest issue (April, 2009) includes these research articles:
Mortality of HIV-Infected Patients Starting Antiretroviral Therapy in Sub-Saharan Africa: Comparison with HIV-Unrelated Mortality
Influence of Rapid Malaria Diagnostic Tests on Treatment and Health Outcome in Fever Patients, Zanzibar—A Crossover Validation Study
Multiple Origins and Regional Dispersal of Resistant dhps in African Plasmodium falciparum Malaria
If you are interested in publishing in PLoS Medicine, please go to their web site for information.