I just happen to know of one: I was recently in Arusha, Tanzania, and was quite taken aback by the mountains of used shoes on sale in the local market. My guide said that this was quite standard and that in the lead-up to Xmas many people would be buying shoes at these stalls.

So it seems that there is a ready market for used shoes and they would be an easy item to fence. Can't imagine there's much margin in it though.