http://en.wikipedia.org/wiki/United_States_presidential_line_of_successionThe Presidential line of succession, as specified by the United States Constitution and under United States Code Title 3, Section 19 (a.k.a. the Presidential Succession Act of 1947) is currently:
Vice President (Richard B. Cheney)
Speaker of the House of Representatives (J. Dennis Hastert)
President pro tempore of the Senate (Ted Stevens)
Secretary of State (Condoleezza Rice)
Secretary of the Treasury (John W. Snow)
Secretary of Defense (Donald H. Rumsfeld)
Attorney General (Alberto Gonzales)
Secretary of the Interior (Gale Norton)
Secretary of Agriculture (Mike Johanns)
Secretary of Commerce (Carlos Gutierrez, ineligible)
Secretary of Labor (Elaine Chao, ineligible)
Secretary of Health and Human Services (Michael Leavitt)
Secretary of Housing and Urban Development (Alphonso Jackson)
Secretary of Transportation (Norman Y. Mineta)
Secretary of Energy (Samuel W. Bodman)
Secretary of Education (Margaret Spellings)
Secretary of Veterans Affairs (Jim Nicholson)
Note that, as of early 2005, the Secretary of Homeland Security has not been put into the line of succession. Senate Bill 442, approved by the Senate on July 27, 2005, would, if it were to become law, place the Secretary of Homeland Security after the Attorney General and before the Secretary of the Interior in the line of succession. That bill and a companion bill, H.R. 1455, are currently pending before the House of Representatives' Judiciary Committee.