Terry Gross

Wilson is a former career diplomat, serving from 1976 to 1998. He had diplomatic posts throughout Africa and was ambassador to Gabon. Wilson was the acting ambassador to Baghdad when Iraq invaded Kuwait in 1990. President George W. Bush, in his 2003 State of the Union address, stated that "Saddam Hussein recently sought significant quantities of uranium from Africa." But in February 2002 Wilson investigated reports of Iraq's attempt to buy uranium from Niger, and found no evidence of such an attempt.

Singer, an analyst at The Brookings Institution, is the author of the book Corporate Warriors: The Rise of the Privatized Military Industry. He'll discuss the use of private military contractors in Iraq, especially in light of the abuses at the Abu Ghraib prison where civilian military contractors were involved in interrogations. Singer is an Olin Fellow in the Foreign Policy Studies Program at the Brookings Institution and coordinator of the Brookings Project on U.S. Policy Towards the Islamic World.

Patterson's book Brown v. Board of Education: A Civil Rights Milestone and its Troubled Legacy looks at the historic Supreme Court case and its aftermath. Patterson also wrote Grand Expectations: The United States 1945-1974.

In 1949, when he was 24, Greenberg joined the Inc. Fund, which would later be called the NAACP Legal Defense and Educational Fund. He worked on some of the most important civil rights cases, including representing Martin Luther King, Jr. He also led the Fund's campaigns to help integrate the University of Alabama and the University of Mississippi. With others, he tried the Delaware and Topeka cases of Brown v. Board of Education. His memoir and history of the NAACP Legal Defense and Educational Fund is called Crusaders in the Courts: Legal Battles of the Civil Rights Movement.

He plays Niles Krane on Frasier, a role for which he won an Emmy. Pierce has also appeared in many films, including Bright Lights, Big City, Little Man Tate, The Fisher King, Crossing Delancy, Sleepless in Seattle and Nixon. He was recently the voice of Abe Sapien in Hellboy.

NBC's Frasier has its season finale on Tuesday. The character originated on another hit show, Cheers. Grammer got his start in classical theatre, but he's best known for his comic gifts.

As the show winds down, Lloyd discusses the popular sitcom. The show debuted in 1993 and won many awards, including a Peabody.

Underhill studies and tracks the habits of shoppers in order to learn the best way to lead them to make purchases. His retail consulting firm, Envirosell, has helped big-name companies such as McDonald's, Levi Strauss and Blockbuster to study their customers' browsing and buying habits. He's the author of the book Why We Buy, and the new book Call of the Mall.

The demand for oil increases each year, but the supply is not inexhaustible. Experts predict that within 30 years our oil energy sources will be depleted. In his book, The End of Oil: On the Edge of a Perilous New World, Roberts looks at the implications for the world in terms of the economy, politics and the environment, and what alternatives exist for oil. Roberts writes about the energy industry for Harper's magazine and for other national publications.

Carley is the executive director of GRASP, The Global and Regional Asperger Syndrome Partnership. In 2000, he and his then 4-year-old son were diagnosed with Asperger's Syndrome. GRASP works to educate the public about the disorder.