The Pew Forum has published an extension report on the religious beliefs, practices, and affiliations of African-Americans.
While the U.S. is generally considered a highly religious nation, African-Americans are markedly more religious on a variety of measures than the U.S. population as a whole, including level of affiliation with a religion, attendance at religious services, frequency of prayer and religion’s importance in life.
See A Religious Portrait of African-Americans by The Pew Forum.