[Ed. note– see Eric’s post about shipping art for more]
Eric, Libby and I discovered recently that the U.S. Postal Service had manufactured a cardboard box just for us. The little Priority Mail box was a complete and perfect match for the book we just made. (It also works for a small batch of homemade cookies, I found out the other day when I shipped some off to my valentines.) $3.95 and 2-day delivery.
Of course the niche market for this box is rather restricted. Apart from cookies and a small book, you probably can send a video (bubble wrapped for security) or maybe some baby booties. I mention this knowing some day you — and others — will have a need for this box.