If you haven't seen these three films from Common Craft, I think they are great introductions for educators, parents, and others who are not familiar with these interactive Web 2.0 technologies:

You'll notice that the links are to the dotSUB versions of the videos (thanks, Wesley!). dotSUB is a fantastic new service that uses volunteers to create video subtitles in different languages. I just uploaded Did You Know? 2.0 to the site. Awesome!