I’m not very well informed about plays, but there’s some great literature that i can recommend.
W.E.B. Du Bois, The Souls of Black Folk. It’s not a novel, but i believe it is literature in the true sense of the word. Some of the chapters—essays really—are very moving.
Richard Wright, Native Son. Fanatastic novel of racial politics and class relations, written in 1940, and set in Depression-era Chicago. Highly recommended.
Ralph Ellison, Invisible Man. Another powerful novel about race in modern America, this book was written in the late 1940s.
Also check out work by James Baldwin, with Go Tell It on the Mountain high on the list.
There’s plenty more, but these are authors and works that come immediately to mind, and that reflect the fact that my interests are, in general, more historical than literary.
You have already mentioned Maya Angelou, Alice Walker, and Toni Morrison, and my knowledge of other black women authors is not very strong. One that i do know about is Zora Neale Hurston, who was a contemporary of Richard Wright. Works like Their Eyes Were Watching God made her probably the best-known black woman writer of her time.
Hurston has been somewhat marginalized in the post-war era, because her novels were rather apolitical, and were not explicitly directed at issues of race relations in America, the way that Wright’s and Ellison’s were. Many blacks, especially in the Civil Rights era, wanted literature to deal directly with race and racism, and Hurston was seen as something of a sellout by some. Her own political conservatism and criticism of some Civil Rights activists didn’t help her cause.
If you’re interested in going back further, and looking at works by black women of the nineteenth century, you might check out this site. Some of the work is fiction, and some is non-fiction, but it is all historically important stuff.