Hi, Elizabeth! The best shops are in Franklin. The Stitcher's Garden is right on mainstreet. It's horribly overcrowded, but she has everything you could ever hope to find -- it just may take time to find it! The other shop in Franklin is much smaller and neater. It's cute, but doesn't have as much selection. It's only a mile or so from downtown on Columbia and is called Quilting Squares.
There are two shops in Lebanon. Lebanon Sewing and Vacuum Center has a decent selection of fabric and books. Quilt Emporium is a nice shop -- great atmosphere -- although the only time I ventured in there the customer service was HORRIBLE! The owner (and only one in the shop) didn't even acknowledge my presence and I was her only customer. Needless to say, I didn't buy a thing.
I have also heard that Harpeth Clock and Quiltworks is nice, but I haven't been there. It's just West of town on I40.
Here's a list of shops in TN, but I think it may be slightly outdated: http://www.thangles.com/TN.html
What part of town will you be staying in?
Let me know when you're going to be in town and if you need a tour guide!