How do I sell a wedding dress and a matching little girl's dress?

Have you tried eBay or
Craigslist? Both sites offer many opportunities for resale
of used (as well as new) items. You can search eBay to get a better idea of asking and
selling prices, and there are thousands of other similar items being sold there at all
times. This may not be a guarantee that your item will sell, however. My wife has
searched eBay for wedding dresses herself, and though there are many bargains to be
found, asking prices and reserve prices are not always met. If you have a quality item
(especially with the matching little girl's ensemble), your chances may be better.
Craigslist is a free service used specifically for local sales, and you may find that it
might be a better fit for your items. It won't cost you any out-of-pocket fees, and the
buyer can pick it up personally. You might want to consider listing your dresses on both
sites at once. You can always cancel either of them if the items sell. Good
luck.