I use PaPal shipping exclusively. Everything that weighs under 13 ounces goes via USPS First Class Mail. The rates are very reasonable AND a delivery confirmation is only $.18.
All packages that are over 13 ounces go out USPS priority mail or USPS Flat Rate.
International orders are shipped USPS International Parcel if they are under 4 lbs. or International Priority if they are over 4 lbs.
My postal scale is one of my most important pieces of equipment
. Not only for weighing outgoing packages, but also for weighing furkids, food portions, and various "things" for the boys.