father of modern online bookmarks managers.
free del.icio.us clone. we use it for bookmarks.sickos.org.
another free online bookmarks manager. written in python.
"The above tag cloud shows the popularity, frequency, and trends in the usages of words within speeches, official documents, declarations, and letters written by the Presidents of the US between 1776 - 2006 AD."
With the Tag Clusters project I was looking at how a hierarchy or faceted system can be automatically generated from a set of tags or a folksonomy*.
Insipid is a Delicious clone written in Perl.