Web 2.0... maybe things have been written about that topic... but why reading pages when you can watch a video?
Here are 2 nice video that are trying to explain what Web 2.0 is about:
That video is a very good introduction of the topic, but a bit boring.
Then next one doesn't cover all the aspects of the web 2.0, but focuses on the most important thing: content is more important than its form
And there are a lot more video on YouTube about that topic.