Wow, what a great thread, female jazz singers are my obsession, to the point it even makes my wife jealous. Already well-recognized here is who I think is the greatest living female jazz artist, Casandra Wilson. My only complaint is it seems her recording engineers think undefined bass is the way to go (EVERY album is like that). Her album with the wonderful pianist Jacky Terrason "Rendezvous" is a jazz great. Lizz Wright, already mentioned, is another artist with huge potential.
But there's other major talent. A few years ago Jeanie Bryson did one of my favorite albums, "Jeanie Bryson sings songs of Peggy Lee." I don't think I've ever heard a more sensuous, sexy album with lyrics like "Some cats know how to stir up a feelin' . . . they keep foolin' around until your halfway to the ceiling . . some cats know how to make the honey flow." Whew!
Just yesterday I got in the mail a group I'd never even heard of (don't you love Amazon's used library?), "Dave's True Story," doing the album "Nature." The vocals are by the lovely Kelly Flint, who is also a non-jazz solo artist. A truly great album, every song.
Another new discovery, and surprise, is the album "Swing" by Suzy Bogguss, who normally does country stuff. Wow, I hope she gives up country forever. Every song is impeccable, and the album's sound engineering is first class.
Some people don't know Natalie Cole has done a couple of albums of jazz standards. Her "Stardust" album is still my test CD for new component/cable changes because the sound engineering is perfect (especially "What a Difference a Day Makes").
The ladies who sing for Manhattan Transfer do great swing jazz, and Basia is great with Matt Bianco doing Latin Jazz on "Matt's Mood."
Some other good artists include Sara Gazarek, Cheryl Bentyne, Shirley Horn, Dianne Schuur, some of Patti Ausin's stuff, Linda Ronstadt!!!, Kitty Margolis, Pink Martini (tho not strictly jazz)...
Someone I listen to often who seems a little overlooked as a jazz singer is Brenda Russell. Some of her songs are sort of on the border since a few make it to pop music, but she is an amazing musician. Consider her impressive album "Paris Rain," where she wrote every song but one. The song "Love and Paris Rain" is downright mystical jazz, if there is such a thing, an absolutely hypnotic masterpiece.
