Dlowan -- long, ugly story. A man named Joseph Wilson went to Africa at the CIA's request in early 2002 to investigate whether Niger supplied raw uranium (the infamous "yellowcake") to Iraq in the 90's. He concluded at the time that no such thing had taken place, and then after Bush talked about it (I forget now which speech), wrote an Op Ed in the NYT about nohow, no way.
Shortly thereafter, his wife, an undercover CIA operative, was "outed." Her name was given to a columnist named Robert Novak. WHO gave the name is at issue. There is speculation that it was a leak from Cheney's office.
http://www.nytimes.com/2004/02/10/politics/10LEAK.html