Amazon Warehouse Deals is how Amazon resells items that people return, that can't be resold as new.
They are often very heavily discounted (50% seems to be the norm, can go higher), and they are sold under Amazon's normal returns policy - usually free returns. You can find things like Clarks Desert Boots, Chippewas, Red Wings, Allen Edmonds etc. in random sizes, and the stock seems to be updated fairly frequently (a few times a week). You can search for stuff here: http://amzn.to/1hZDjqj
Unfortunately you mostly have to get lucky to find your size.