No, Timothy Geithner, Barack Obama's former secretary of the treasury, is not a Jew.
Geithner was president of the Federal Reserve Bank of New York. He is the son of Mr. and Mrs. Peter F. Geithner of Larchmont, N.Y.
According to the Times, he is married to Carole M. Sonnenfeld and has two children. The Rev. Thomas Keehn, a United Church of Christ minister, officiated at his wedding in 1985.
On 11/22/2008 I received an email reply from Geithner's father-in-law, Prof. Albert Sonnenfeld, confirming that, "Geithner (is) not Jewish, (he was) raised Episcopalian, but (is) hardly religious now."
The reference in Wikipedia that previously (up to 11/2008) said he is a Jew - was removed. See the discussion.
Update 5/14: Geithner has a new book: Stress Test: Reflections on Financial Crises and was profiled in the Times magazine.