Camtasia Studio is a very useful tool that can record every video clip if I want to record it. I sometimes felt uncomfortable that I couldn't download video clips on some websites for my classes not for the commercial purpose. But I can do that.
I may also use the screen capture site, http://www.screencast-o-matic.com
For the exercise, I captured one about Jamie Oliver. I'm a big fan of him.
+ It's Jamie Oliver's TED show and he got the TED prize. I like his idea, speaking style and appearance, of course : -)