I thought that maybe some Acaeum members (those that sell items particularily) could share their packaging methods in this thread. Maybe, just maybe, some industrious new seller might learn something. The last straw for me came when a very nice copy of M1 Into the Malestorm I won came water damaged/creased/rolled/spindled because the seller used only paper thin envelopes to send it in.
Here's my method and envelope mailing typically costs me .30 to .35 in supplies:
1. All modules/books are bagged and the bag taped shut.
2. I purchase 48 x 96 inch sheets of corrugated cardboard pads and cut them down to 9 x 12 inch sections (slightly larger than most modules/books). Or just cut up some old boxes in the garage.
3. For envelope shipping I simply sandwich the modules/books between 2 pieces of cardboard and tape all 4 ends. Depending on book thickness I can usually get 3-5 modules into the cardboard package and still have it fit the envelope.
4. I use standard 10 x 13 mailing envelopes.
5. I do have to modify the size of the cardboard to fit Priority Mail flat-rate envelopes.

I've been known to offer to mail my own packing supplies to the seller to ensure the item is packaged safely.
The end result is a package that is fairly rigid and difficult to bend. Unless the postal carrier uses super-human efforts he/she cannot force the package into a mailbox. Plastic or mylar comic bags are improtant to help resist moisture damage.
In my opinion, bubble-mailers are a waste of money and they don't protect softcover modules from bends and need to be re-inforced. Priority mail flat-rate envelopes are easily bent by themselves.
For large orders consider breaking up the merchandise into 2 smaller boxes and strap or tape the boxes together so you are shipping only 1 package. Ideally boxes should weigh no more than 10-15 lbs. Large, heavy boxes are typically dropped on conveyer belts by mail sorters. Packages that contain box sets and books/modules should be packed with the box sets on or near the top to prevent crushing.
Any comments/ideas?