National Museum of African Art
According to the National Museum of African Art's mission statement, the museum ". . . fosters the discovery and appreciation of the visual arts of Africa, the cradle of humanity."
While African art, as differentiated from African American art, is not necessarily directly applicable to teaching American history, it should not be written off as irrelevant. After all, the Middle Passage, slavery, and the Great Migration are major historical U.S. institutions and events which all involved Africans and/or African Americans. This art can be used to discuss the cultures in which today's African American populations originated, and how these cultures played into their lives in the United States—in the past and today.
A good starting point for educators is, naturally, the teacher resources. The page includes five curriculum resources, covering Mali, Cote d'Ivoire, Ghana, and the artist Gavin Jantjes; a contact to help you develop curricula involving African art; VHS loans (by mail); and select artist interviews, among other resources.
Another great destination is the museum's collection of virtual exhibits. These are divided into traditional, contemporary, and combination sections. A quick glance reveals highlights such as "Playful Performers," an exhibit on child play; "The Art of the Personal Object"; "Wrapped in Pride: Ghanian Kente and African American Identity"; and "Transatlantic Dialogue: Contemporary Art in and out of Africa."
If you are teaching younger students, the website also offers activities such as coloring or designing symbols and masks, listening to traditional music, and several "seek and find" and trivia activities.
Have something specific in mind? You can, of course, always search the collections. Search options include type of artifact, use, imagery depicted, culture of origin, and more.
Finally, if you're in the DC area, consider scheduling a field trip or outreach program.