Income from Foreign Sources

If you receive income from foreign sources, you still have to pay tax on it. A U.S. citizen or resident alien generally has to pay tax on his worldwide income. However, if you actually work for an extended period in another country you may be able to exclude a significant portion of your income—for 2008 the exclusion is for $ 87,600. To claim the exclusion you would need to file Form 2555.
http://www.1040.com/taxxcpa/