del.icio.us and Foxylicious

Tagging has arisen as a way for users to organize data in way that makes sense to them. Tags are keywords that represent categories, and objects with identical tags are linked and can be searched.

Social bookmarking websites allow users to share hyperlinks with other users; del.icio.us is the most popular of these sites because of its simplicity and ease of use. Other social bookmarking sites have been created that offer expanded or niche services such as the tech-oriented digg.com, which lets others users vote and make comments on submissions.

A user's links can be integrated into the Firefox browser using the Foxylicious extension allowing del.icio.us bookmarks to be updated daily on the user's computer. Foxylicious can also create subcategories from tags when bookmarks are tagged with identical prefixes separated by a user-specified character called a delimiter (i.e. college.classes and college.events where "." is the delimiting character).

Recently, del.icio.us has introduced an experimental function called tag bundles can also be used to group tags. Tag bundles are created from a user's profile http://del.icio.us/settings/username/bundle. Starting with version 0.6 Foxylicious has added support for tag bundles. One potential limitation of tag bundles is that they only offer one level of hierarchy.