This is a nice and relatively easy guide to understand for those budding young composers/musicians. Even though I already knew how to read music, this guide easily summarizes the basic things you need to know.
This is pretty much meant to be basic, but you could expand the information with teaching the different components of music, such as quarter/eighth/sixteenth notes, chords, majors/minors, the possibilities are almost endless.
There are some glitches in the flash though: besides the overlapping music, when you try to go back on the TABs page, only the text will go back. You will need to press the back button many times and you cannot press the continue button.