One country-oriented female vocalist I've always recommended, and about whom received generally good feedback, is Tift Merritt. There's one song I love by her that takes country and dabbles it in classic 60's soul.....Good Hearted Man
She also has some nice versions of another song I like, Stray Paper, on youtube.
I just recently picked up the Alison Brown CD "Stolen Moments." Similar at times to Alison Kraus, but also delves into some jazzier sounds, and is a great listen.