I just uploaded a new Video, "Standard Deviation". It is part of the playlist on Variation, Variability, Dispersion, and Spread. Below are the 5 Keys to Understanding for this concept. See the videos page of this website for the latest status of available and planned videos.
Andrew A. (Andy) Jawlik is the author of the book, Statistics from A to Z -- Confusing Concepts Clarified, published by Wiley.