C.S.
Wow, this sounds familiar! I wore the gown of my dreams (Badgley Mischka for Pronovias), and then it sat in my closet for a few years. I ended up putting it on eBay, and I made back 3/4 of the money spent originally. All it takes is writing a detailed description and adding a few pictures. (A reserve price on something like this is probably a good idea, too.) Then, after it was paid for by the buyer, I just dropped it off at FedEx.
I have also heard of a wedding consignment shop in Atlanta, but I cannot remember the name. I chose eBay, though, since it provided a larger market, which, especially in this economy, might help you make a little more money.
Hope this helps! Good luck to you!