This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
From Joan :
When I am shipping things, I either freeze them or pack them very well.
For example, with yeast breads, rolls, etc., I generally freeze them and ship
them off with express delivery. That obviously works best if it will be
delivered within 48 hours.
For items like cookies or tender pastries, I generally find an airtight
container for them and then pack them very carefully with lots of waxed
paper between the individual items. Make sure they're packed snugly but
not enough to crush the items when you put on the lid. Cookies travel very
well this way, and some cookies also freeze pretty well so you can ship
them in that state to help preserve them.