Yeah, but which half? But Which Half?!?!?
EDIT: That was actually in response to Vicki's post, not yours, but it's funny seeing it applied to yours.
Neko Case and Gillian Welch are new Americana or alt.country, aren't they? Is that what interests you? The following suggestions are based entirely on that premise, because other than that, I have no interest knowledge myself in any of those other genres.
I would definitely check out Allison Moorer.
No Depression by Uncle Tupelo is considered a turning point.
Early Wilco.
Jim White is fun.
The Devics are absolutely sublime.