I love the real twangy, honky-tonky classics, like Johnny Cash and Patsy Cline. You can’t go wrong with them!
But lately, I’ve become a huge fan of alt-country, cowpunk, Americana, whatever you want to call these hip subgenres. People have already mentioned Wilco (fantastic band) and Son Volt, both of which evolved from the great Uncle Tupelo. I’m not a huge expert, but I know they all deserve their reputations.
Neko Case is a fantastic alt-country chanteuse, and I cannot recommend her album “Blacklisted” highly enough. It is very dark, moody, sexy, smoky, cinematic–“twang-NOIR.” OpalCat, you mentioned liking Siouxsie and the Banshees on another thread, if I’m not mistaken. While Neko Case doesn’t have much in common with Siouxsie musically, I can see how a fan of one might appreciate the other, particularly if you like Tom Waits, Nick Cave, or similar “dark” artists.
Other alt-country-esque bands I’ve enjoyed (many of whom harken back more to classic country than any of the hat-wearing flag-wavers and warbly supermodels of modern pop-country music) are the Old 97s, BR549, Bastard Sons of Johnny Cash, the Mavericks, Hank Williams III (who brings a lot of punk influence to the table), and the great Mike Ness, the rockabilly-influenced singer of rootsy punk band Social Distortion.
Then there’s the entire subgenre of Western swing, popularized in the '30s and '40s by Bob Wills and the Texas Playboys. It’s classic cowboy music blended with big band swing, and it’s lots of fun. Asleep At the Wheel is probably the best modern Western swing band, and Lyle Lovett actually has some good Western swing on his “Large Band” albums.
The O Brother, Where Art Thou? soundtrack should have some good rootsy-folky-American music for you, like a beautiful lullaby sung by the aforementioned Alison Krauss, Emmylou Harris, and Gillian Welch. Loretta Lynn, another famous country singer who was most popular in the '70s, just came out with a new album, “Van Lear Rose,” produced by Jack White of the White Stripes. I’ve heard fantastic things about that as well.