http://del.icio.us/ — a social bookmarking app
Users assign tags to their bookmarks as they are stored
People tend to use similar tags
The set of bookmarks associated with a given tag are available to anyone
Provides a good idea of what is currently important to people interested in a certain topic, eg. PHP
Sets of bookmarks are available as HTML, RSS feeds, and via a REST API
The app we'll develop will use the RSS feeds to retrieve and present sets of del.icio.us bookmarks from the command line.