We use the US Postal Service for all foreign shipments, and most domestic shipments too.
My experience - UPS and Fed Ex are extremely more expensive on foreign shipments. And as Will mentioned there's the brokerage fees to contend with, which don't come into the picture with the US Postal Service. Fed Ex may handle the parcels a little more carefully, but only marginally so; UPS handles the parcels worse than the US Postal Service ... reminds me of the old Samsonite luggage commercial with the luggage being tossed about by monkeys. All 3 offer tracking and insurance. Here in Ventura the US Postal employees are also the most knowledgeable and professional, they know exactly which forms need to be filled out, etc. About two minutes at the counter and the transaction is complete. Fed Ex employees are second, but they fumble around trying to figure out foreign shipments. A transaction takes about 5 minutes. The UPS store is run by morons, shipping with them leaves you wondering if the package will make it to its destination. The transaction time is even longer than Fed Ex.