Here's my consumerist Circle of Life: I sell stuff on eBay, then use that money to order new products from Amazon. And the cardboard boxes my Amazon purchases arrive in, after undergoing a slight operation, often go back out the door laden with eBayed stuff--just cut the packing tape off of the bottom flaps, pull the glued tab free from the inside, turn the box inside out, re-tape it and boom, you've got a new box.
I thought everyone knew about this box-flipping trick, but apparently not; a company called Salazar Packaging is patenting their own "Globe Guard Reusable Box," which is essentially a regular cardboard box except they've made the glued tab in the middle easier to remove (it's perforated) and they provide an adhesive strip to re-glue the tab inside out.
I don't think it's much more difficult to cut and re-tape the box yourself, but I guess anything that encourages people to re-use things is good. Here's a video showing Salazar's product, and you definitely don't have to sit through the entire six minutes--the demo starts around 1:45: