The Washington Post website includes a RealPlayer file with a CNBC interview of Dana Priest, who broke the story of the Senate and House intelligence committee members' refusal to submit to polygraph interrogations in the ongoing leak probe:

http://www.washingtonpost.com/wp-srv/mmedia/nation/080102-12v.htm

If Congress won't take polygraphs, why should anyone else?

PROAc,

Congressional staffers are not compelled to submit to polygraph "testing" as a condition for a top secret clearance.

Note that apart from the Foreign Service/State Department, other agencies do grant top secret clearance without a polygraph seance, for example, the Department of Defense (though it may require a polygraph depending on the kind of information to which the individual will have access).