I thought this might be of help to US people out there who sell their own inventory on auction sites, websites, etc.
If you go to Link hidden: Login to view
and click on shipping supplies (I know you can access it through the top navigation bar drop down menu), you can order various types of shipping packages for free through the postal service.
That I can think of off hand, you can get Priority Mail supplies like boxes, envelopes (flat and the papery cloth ones), triangular tubes, window envelopes, shipping labels, stickers for when you use your own box, signature and delivery confirmation forms, etc..., Express mail - about the same as priority mail.
I believe they have other stuff too. What's really nice is you sign up for free with them, place your order (some things do cost, like the prepaid flat rate envelopes), and unless you order something that does cost due to prepaid postage or rolls/books of stamps, they'll ship you your supplies for free through parcel post.
It took me about a week or so to get mine. Got them today delivered right to my door.
Also through the USPS website, you can print postage from your computer, paying with a credit card through the site, and schedule a pick up of your package right at your front door.
You can also get free supplies through Link hidden: Login to view
but you have to sign up for a special account and give them a credit card to keep on file. The supplies are free and are shipped free. The credit card on file is for them to charge when you print postage from your computer. You can also schedule pick ups through their website.
I think fedex Link hidden: Login to view
has the same type of thing, but I'm not sure.
Hope someone finds this useful. :D