Great topic!
Well, many good mentions here so I'll just tack on some of my favs that haven't been listed above since there are plenty of good lady crooners too

:
In no particular order since all of the artists below are all so gifted and talented in their own way that to place them in a “best to worst” would be shameful:
Soft, sweet female crooners:
~Tony Braxton (“Unbreak my heart” is sooooo beautiful and many others, her voice takes you to the edge and back).
~Sarah McLachlan (Her voice is just so lovely to listen to and "In the arms of the Angel" still can make me cry when I hear it).
~Sade (Beautiful, sultry, sexy and utterly feminine voice).
~Natalie Umbruglia (She has a certain vulnerability to her voice that is hauntingly beautiful).
~Shania Twain (Her voice is so pretty it almost tickles to listen).
~Anita Baker (A voice that is like a heavenly instrument if ever there was one).
Strong, powerful female crooners:
~Celine Dion (I know she’s been overplayed to death but boy can she hit those notes)!
~Alannah Myles (Black Velvet was her big hit…I dunno if she’s come out with anything since then but her whole CD rocked)!
~Annie Lennox (Her voice tells you like it is in no uncertain terms

).