This instructional video explains the Library of Congress Numbering system.
http://www.youtube.com/watch?v=4djuA5ZfOWE
You tube is an easy way to share a short event such as a parade or a self-made informercial. Many of the item are of aappeal only to the creator and are of low quality. Some are similiar to a real commercial and are fairly well done. They can also be informative and instructional and entertaining. Dance demos can be found as well as how to do household projects. I am not surprised at the growing popularity among adults and youth.
Libraries could make their own as a virtual tour for patrons to introduce them to staff, facilities and services.