There are many non-governmental organizations, both big and small, that are concerned with AIDS in Africa. All of these are organizations that are trying in some way to prevent the spread of AIDS and/or to alleviate the problems caused by the disease.
For example, there is UNICEF. UNICEF is a UN organization that tries, among other things, to reduce the rate of AIDS transmission and death from AIDS in Africa. An organization doing similar work is the Bill & Melinda Gates Foundation. A third NGO that works on this issue (again, among other things that it does) is Doctors Without Borders. This group focuses more on the treatment of people with HIV/AIDS, providing antiretroviral drugs to help these people have better lives.