African American Heritage: Hosted by the National Parks Service, this site allows you to visit museum exhibits and read indepth histories of famous African Americans. Be sure to click "visit a multitude of park sites" to visit the individual pages of parks related to African American history like the Selma to Montgomery National Historic Trail and the Martin Luther King, Jr. National Historic Site.
Civil Rights History Project: A collection of oral histories of participants in the struggle for civil rights. The site also includes a collection of essays related to the subjects of the oral history interviews.
Digital Schomberg: A collection of links curated by the Schomberg Center for Research in Black Culture. Includes links to journals, books, maps, images, etc. (all free and open source).