There are many primary sources on the Internet. Here is how to find them.
For example ~ Go to a search engine like Google ~ or try the Meta Search Engine Vivisimo which breaks the sites into categories with its 'clustering' feature.
      In the Search window using the Boolean method, type in document OR primary source AND African Americans. 
      See below for just a few of the documents and primary source sites retrieved on the topic of African American History.
               Africans in America
               African American Odyssey
               Born in Slavery
                   Documenting the American South
               Voices From the Days of Slavery: Former Slaves Tell Their Stories 

Here is an index of primary sources from Springfield Township High School Virtual Library
                   Primary Sources for the Study of African American History

For a better understanding of primary and secondary sources, read the following.
                Primary Sources from Springfield Township High School Virtual Library created by Joyce Valenza.
                    Why Study History Through Primary Sources?