Chris Crawford is one of the greatest game designers who ever lived. He inspired a great number of designers over the years. But he's more than just a designer. He is also a teacher, and a darn good one at that. He knows the language of interactivity better than most, and is very effective at passing it on to others. Sure he is a bit bold and arrogant, and maybe a bit eccentric (Okay, he's extremely eccentric), but that's because he has a LOT of experience. He's known as the "Grand old father" of game design, and is renowned for his books on game design.
Here's his most famous lecture, split up in 5 parts.
Part 1:
http://www.youtube.com/watch?v=_04PLBdhqZ4
Part 2:
http://www.youtube.com/watch?v=Ymu4A9861Ck&NR=1
Part 3:
http://www.youtube.com/watch?v=GpW0fZ0390M&NR=1
Part 4:
http://www.youtube.com/watch?v=n7N_Ju1L_Mg&NR=1
Part 5:
http://www.youtube.com/watch?v=xqMwmdvf8v0...feature=related