If you've ever wondered about the process your packages go through once they leave your hands, USPS has created a video that visualizes each step along the way:
How to: Address USPS domestic mail
How do I complete a customs forms to ship overseas?
ShippingEasy Rates: what you can expect to save on USPS postage
What mail classes are available through ShippingEasy?
ShippingEasy Quick Start Guide