About the Del.icio.us API
Clay Shirky article based on two talks he gave in the spring of 2005.
Popular Tags on Flickr Photo Sharing.
My comment suggested that the only sin of tag clouds was popularity. But the problems with tag clouds run deeper. Jeffrey Zeldman, 4 May 2005.
Like mood rings and fanny packs, like mullets and the Macarena, the weighted tag clouds meme popularized by Flickr and Technorati is about to cross a permanent cultural shame threshold. Jeffrey Zeldman, 19 April 2005.
Freetag is an easy tagging and folksonomy-enabled plugin for use with MySQL-PHP applications. It allows you to create tags on existing database schemas, and access and manage your tags through a robust API.
Thomas Vander Wal coined the concept folksonomy. Here, he explains the concept.
Derek Powazek, on tagonomy.