Flying First Class for Free They're not rich, but extreme airline miles collectors can fly around the world. Memory Champ Shares Brain Tricks Nelson Dellis can memorize a deck of cards in 63 seconds. A look at what will happen to your taxes if the Congress doesn't come to an agreement. Family Dollar CEO Howard Levine talks about how dollar stores have thrived in a down economy. 'Back to the Beginning': Ark of the Covenant Christiane Amanpour retraces the mysteries of the Bible in her ABC special. Two Hollywood heavyweights talk with"Nightline's" Cynthia McFadden about their new movie. Michelle Obama Answers Kids' Questions Part 3: First Lady answers questions from first graders with special connection to White House Christmas tree. Tracking Elusive Narwhals in the Arctic Part 1: These creatures known as the "unicorns of the sea" are threatened by climate change. Close Call on the Arctic's Melting Sea Ice Part 2: A desperate scramble over a massive crack in the sea ice creates a scary situation. Climate Change Threatens Arctic Life Part 3: Warming global temperatures are melting critical sea ice.