I use the 32 oz 6.75 containers for hatchling balls at shows but not for shipping. half pint deli cups for hatchling colubrids, 8X12 bags for hatchling balls or subadult colubrids, 12X30 ( I like them a little deeper so I can tie a good knot in them) for most adult colubrids or balls, 16X32 or king size pillow cases for boas/carpet pythons and heavy duty nylon laundry bags for the burms or big boas.
Also, if you're going to be traveling across country for a long distance and you have a large collection, invest in a bunch of cheap chest coolers at walmart. I know several people who have lost animals to overheating while transporting their collection in the back of a truck or the trunk of a car.