If you haven't seen this series of clever, simple, short and clear videos you are in for a treat. Common Craft : http://www.commoncraft.com/
has developed number of short videos that are going viral on YouTube and elsewhere.
You can get to the source (and possibly by pass school filter problems with You Tube by visiting their website.
They also have vids on social bookmarking, comparing social networking to online communities, and the differences between blogs and and message boards.
Many educators need to understand these concepts. Many don't have a clue. The In Plain English Series is a quick way to give folks a multimedia based eureka moment. I'm linking them to my online classes about web 2.0 because they work!
Hope this helps,