Alison Krauss.
I finally got around to listening to Alison Krauss and the Union Station's New Favorite last night. Wow.
Alison Krauss sounds like Dolly Parton without all the bad producers. She was one of the female vocalists from the O Brother Where Art Thou? soundtrack -- that's how I'd heard of her -- and the man who does the singing voice for George Clooney is part of the band.
I do not recommend this album for anyone who genuinely likes most of the contemporary country music on the radio, but for people who like bluegrass, folk, blues, and old country. Listen to the samples here.