Rivendell Bicycle Works has the best shipping department ever. They always fit what you order into the smallest sized thing possible, re-using materials as much as possible.
This is probably obvious, but the absolute easiest thing possible for them to pack is a Wald basket, plus a bunch of things that fit inside a Wald basket. They have a box that fits a Wald basket perfectly, and if all your stuff fits into a Wald basket, then all your stuff will fit in that box, perfectly. The basket protects everything, and it's dead easy for them.
My order today was stuff for my son's college-beater bike (UC Santa Barbara):
Wald Basket
Sackville Medium shop sack
Ottolock (for my own town bike)
USB Cygolite
Bill Lindsay
El Cerrito, CA