Before the Big Box stores like Staples came to town, most people in Canada got their office supplies at Grand & Toy. When I was a kid I always searched in vain for the toys; in fact, it was one of the founding partners' names. It's now owned by Officemax. They do a lot of corporate work, and make a lot of deliveries, which uses up a lot of cardboard boxes.
Everybody feels good about recycling, and every company flattens and recycles cardboard boxes. But this kind of producer responsibility from Grand & Toy is a demonstration of how good design can make it easy to reuse. A much better idea. More at Grand & Toy.
UPDATE: OfficeMax has been rolling this out in the USA as well.