My nominations, in unranked order...
k.d. Lang - esp. album Shadowland which is more torch than twang
Shirley Bassey - esp. 1987 single with Yello "The Rhythm Divine"
Lisa Gerrard w/ Dead Can Dance and solo
Sheila Chandra - "Sacred Stones"
Amina Alaoui - "Amours ou Trop Tard Me Suis Pris"
Cesaria Evora
Eefje de Visser - always in Dutch
Snatam Kaur - "Mu Mantra Snatam Kaur"
Azam Ali
Beth Orton
Norah Jones
Rickie Lee Jones - of course
Sarah McLachlan - Dirty Little Secret
Samantha James - Rise
Natania Davrath - Songs of the Auvergne (TAS superdisc)