The USPS is giving away free shipping materials to any American citizen, who simply requests for it. You can receive Priority Mail flat rate boxes, envelopes, shoe boxes, address labels, video boxes, and stickers. Forget paying Staples for boxes and envelopes, the US government is giving them out for free.

You can order boxes and assemble them inside out, hiding the USPS logos. Then you can easily use them for mailing products with UPS or FedEx.

Priority Mail Shipping Supplies
Express Mail Supplies