The current (June 2008) United States ambassador to the Holy See is Francis Rooney. Rooney, a businessman with little diplomatic experience, was appointed to the post by George W. Bush in 2005 as a reward for his work in raising funds for the 2004 Bush campaign. Companies owned by Rooney have also won several large federal contracts under the Bush administration.
Update:
Ken Hackett was nominated by President Barack Obama on June 14, 2013 to serve as the U.S. Ambassador to the Holy See.
The current US Ambassador in Germany is Phillip Murphy.
Current (July 2010) ambassador to Mexico is Carlos Pascual (b. 1931).
Adebowale Adefuye is the Ambassador to the US for Nigeria.
The current US ambassador to the UN is Susan Rice.
A Nuncio is an ambassador for the Vatican.
As of July 2014, Ramon Gil-Casares is the Ambassador of Spain to the United States. He previously served as the Spanish Ambassador to South Africa.
Ambassador Zakaria Haji Abdi is the Current Somali Ambassador To Malaysia.
Nuncio
Matthew Barzun, as of July 2014, is the United States Ambassador to the United Kingdom. The position was established in 1785.
Dame Karen Pierce, DCMG
Papal Nuncio
An internuncio is a papal envoy or messenger but ranks below a nuncio, or ambassador.