There are several nationwide charity organizations which will take used clothes and sell them. Nobody is going to give you credit for new clothes, unless the used clothes are exceptional. Most used clothes have little or no wholesale value.

A simple enough solution to this is to have a yard sale. Advertise it well enough in advance to draw a good crowd and you can sell darn near anything. Donate what doesn't sell to the Salvation Army or Goodwill for a tax deduction. My wife and her sisters do this once a year.

The economics would be better for shoes, assuming they have little wear on them. Shoes are expensive and are hard to find at yard sales, due to the need for an exact fit. If there were a used-shoe recycler in each town with online photos of the shoes in stock, potential buyers could browse within their size (length and width) and type preferences (color, category (sneaker, boot, etc.), and style) and then order online--or drop in and pick up.

This might only be a break-even proposition for the seller, but it would make an environmental organization that sponsored it feel good (due to reducing waste and making things easier for the poor). It could also serve as a publicity and recruiting tool for such an organization.

PS: What would really put this idea on the map would be for the post office to offer a very low rate for items sent to or from registered used-shoe recyclers.