Why some techniques are hidden.
How they are hidden.
The ways in which karate used to be taught.
Some examples of bunkai applications.
http://seinenkai.com/art-bunkai.html
As with all outside sources, I recommend that parents read the articles before deciding whether or not to share them with their kids. I teach students of all ages and maturity levels so this is my way of striking a balance in which this site can be useful to all students.
Enjoy, and post in the comments what you thought of the article!