Came across this TED talk by Arthur Benjamin demonstrating phenomenal mathematical calculations. He starts with squaring two digit numbers and then progresses to three, four and even five digits. Another trick demostrated is guessing (correctly of course) the day of the week, given a date. He has been featured in Readers Digest as well.

Stephen Hawking talks about the big questions facing the universe, viz. how did the universe begin, how did life start and are we alone in this universe.