According to intelanalysis.org, the Government of Singapore has agreed to scan U.S. bound shipping containers for nuclear and radiological materials for a six month trial period. Other news reports list Honduras, the U.K., Oman, Pakistan, South Korea and Hong Kong as participating ports.
These efforts are taken under the auspices of the Secure Freight Initiative, a joint Department of Homeland Security and Department of Energy project. Congress mandated 100% cargo screening of all U.S. bound cargo containers at foreign ports by 2012. This will not be an easy requirement. An official with the Department of Homeland Security admitted that he was "daunted by the prospect of 100 percent scanning in every port".
The federal government's approach to port security after 9/11 have been criticized (by my former Professor at the U.S. Coast Guard Academy) for being "piecemeal". Despite advances in port security, certainly more work is needed to protect the lifeline of the national economy.