Comedian Demetri Martin is probably best known for his appearances on The Daily Show with Jon Stewart. He's also written for Late Night with Conan O'Brien, for which he garnered an Emmy nomination.
He's released a DVD called Person — a version of his one-hour Comedy Central special, which aired earlier this year.
For 25 years, author and journalist Ahmed Rashid has covered Pakistan, Afghanistan and Central Asia.
He files for English language papers including the International Herald Tribune, The Wall Street Journal and The Daily Telegraph. Based in Lahore, Rashid is the author of the bestselling books, Taliban and Jihad.