I was looking at the USPS website but to no avail as to what items are prohibited. Anyone with experience care to share some knowledge on what items are not allowed to be shipped out of the US?
The USPS is generally concerned with hazmat, and ORM-D stuff like fireworks and gunpowder etc. For that you need to use another common carrier like UPS, DHL, FedEx etc.
If you're concerned with technology transfer issues, the U.S. State Department maintains those guidelines.