J.B.
This may be difficult to find in a small Tennessee town, but you never know! You sound like you would love the UU (Unitarian Universalist) church! Many agnostics attend and they invite people of all spiritual paths and faiths to come.
If you can't find one of those, you'll probably need to be somewhat choosy. Pentacostal or fundamentalist Baptist churches, particularly in the South may involve speaking in tongues, fire and brimstone sermons and other things that would most likely make you very uncomfortable.
I would seek Methodist, Presbyterian or Episcopal churches if a Unitarian church isn't around. First Church of Christ/United Church of Christ is also more free-thinking and accepting (note -this isn't JUST "Church of Christ" -be careful there because the two are very different).
As far as dress -it really depends. Many congregations have relaxed dress codes across the board. Typically, in the South, most people dress for church in "business casual" or nice skirts/dresses. If you are considering a church, see if it has a website, and they'll probably address what to wear on it. UU churches are usually more relaxed and you find people in "church clothes" and jeans and everything in between.
It's a great way to meet people if you find the right place. If you go -most services start around 11:00 am on Sunday mornings, but some have two services. You can just walk into the sanctuary and have a seat. Some services will have a greeting time when you can introduce yourself to others who will introduce themselves. Please don't take this the wrong way, but be careful about announcing that you're an agnostic or a former Mormon. Many people in traditional churches have "issues" with both of those. That's why I think you would fare best at a UU church or United/First Church of Christ. IF not that -Methodist, Presbyterian or Episcopal -but know that those 3 have wide variations in belief and practice! Also -at Episcopal churches they do take communion in a very Catholic way -although you don't have to join in -just know that this will happen.
I was curious -here's a UU church in Chattanooga -evidently about 30 minutes away from you:
There's also Cleveland Church of Christ, which IS a United Church of Christ fellowship.
Is Neshoba near you?
http://www.neshobauu.org/index.php?option=com_content&...