Ever had the experience of thinking of something after you've given an answer? Well, I thought of a couple more names that I should have included in my first response. One of the truly great, all-time singers was Mahalia Jackson. Because of her religious beliefs, all she ever recorded was gospel music, but Oh, Lord!, could she sing!! If you can listen to Mahalia without your body moving, you better check your pulse. The first time I ever heard Mahalia in concert in Honolulu in 1962 or '63. She appeared at the Waikiki Shell, an outdoor ampitheater that seated about several thousand people. About halfway through the concert the amplication system died, so she finished the concert without any amplification. Her voice still filled the ampitheater with glorious music - and a friend of mine who lived several blocks away could still hear her! There is a CD boxed collection of Mahalia's music that is excellent, and she is also superb on Duke Ellington's suite, "Black, Brown and Beige". In the folk/jazz vein, there are several remarkable singers from the 1920's, the best of whom was Bessie Smith. You could think of Bessie Smith as the early, "secular" Mahalia Jackson. In the 1960's, Odetta was a sort of reincarnation of Bessie Smith - great raw, moving power. I asked my wife if she had any favorite female vocalists, and she mentioned a couple I hadn't thought of: Maureen McGovern, Annie Lenox (of the Eurythmics), Big Mama Cass Elliott (from The Mamas & The Papas, and an earlier group called The Big Three), Diana Ross, and the Pointer Sisters. In the opera vein, I certainly agree with the mention above of Jessye Norman. She was here in Seattle a year or two ago for the dedication of our new symphony hall, and everyone who attended was absolutely stunned by her singing. I'd also add one other current-generation singer, Eileen Battle. No list will be definitive, but the input on this thread has been pretty damned impressive.