In regards to shipping, I usually re-purpose boxes in which I've received things. I also snagged a roll of bubble wrap from Home Depot. Don't quote me on this, but I think it was $10 for 100 ft. All I know is I bought it about 3 years ago, I've shipped a decent amount of things all over the world, and I still have plenty left.
Get some good packing tape, too. When in doubt, over-pack, don't under pack.
Also, include a note in each of your shipments with the name and address of where the package is going/where it came from. If something awful should happen to the box, they'll still be able to get it to its destination. Hopefully.
Lastly, remember that this is bartertown, so please negotiate, but also be reasonable. The people here generally want to move their product/or buy product, but they don't want to get hosed either. Talk to people and try to find your common ground to make it all work.