In this chapter, you looked at how to use tags to create mashups. I first compared and contrasted how tags are used in Flickr and Flickr’s tagging system is an example of a narrow folksonomy, enabling textual searches to be done over visual media. As a broad taxonomy, involves many people tagging any given bookmark, creating multiple sets for tags for a bookmark. You considered some factors that reduce the reliability of tags and studied specifically the issue of singular versus plural nouns and the role played by syntactic constraints such as spaces, punctuation marks, multiple cases, and non-­ASCII characters in Flickr and You looked at Technorati as an example of a tag-­based search engine as a case study of how to use tags to relate disparate digital content. I showed how you can create a simple mashup of Flickr and using tags to create sets of pictures that intermix your photos and other people’s photos in Flickr. This chapter ended with an example of combining tags with formal classification schemes in the context of books.