Thomas Vander Wal provides an overview on tagging services and outline where there is value in tagging. This focuses on what is different in folksonomy that improves upon tagging, so that it becomes a powerful tool. Thomas provides insights to help answer when to use tagging and/or categories, who should be tagging, the value of a tagcloud (or lack of value) when used properly, and how to create value from tagging to improve the sites and services we build.