Pop Country Sucks... Everyone knows that. However, there are a bunch of really talented country artists out there that I believe many Nine Inch Nails fans would enjoy.
Here is a quick list of suggestions:
Hank Williams III
The Drive-By Truckers
The .357 String Band
These bands don't fuck around. Feel free to give me some feedback, and of course share your own suggestions.
Finally, SavingCountryMusic.com is a good reference to find good country music.
Waylon Jennings Pandora station is pure win.
LOVE the DBT's. One of the best live bands around. Shooter Jennings is pretty badass too. Hayes Carll is a guy I can add to the list. His album KMAG YOYO is one of the best albums of the year and the title track is probably my favorite song this year. I like Jamey Johnson as well, he's just a fucking badass. And even though they're not "Outlaw", Zac Brown Band is probably one of the better mainstream country groups out there.