This video primer on the GTD system was posted on Lifehacker.com - a great personal productivity website. From Lifehacker.com:
"Hyper but lovable author of Getting Things Done David Allen explains the meat of his GTD system in this five minute video, which covers dealing with the "stuff" in your life, reducing your to-do's to simple "widget-cranking," and clearing your mind. Allen comes across pretty frenetic in this quickly-cut together clip, but it's a good primer for folks new to GTD."
Here's the link.