This article was stimulated by an article in Stephen Downes' OLDaily newsletter. So how do you categorise your digital information/documents? Creating a hierachical tree of directories/folders supported by a metadata search of some type is the time honoured solution. Of course you've got to create and maintain the hierarchy and remember to enter that metadata about the content. Dynamic Categories could offer us a better way. As best I understand it, in Dynamic Categorization the metadata arises from the content itself and so the human instead of focusing on generating the metadata focuses on building a content-aware query. Such queries can be stored for reuse and in effect the query results form a category. If you want to try an example of this visit Jon Udell's recent blog article on Dynamic Categories.