A tagcloud is a list of the most popular tags (keywords) used, usually in blogs and RSS pheeds.

Here's an example:
http://www.technorati.com/tags/

Here's a tag cloud taken from Yahoo News:
http://yahoo.theherrens.com/index.php

Note: The larger the font, the more popular the phrase.

We will want to monitor tag clouds for "hot" phrases, as well as looking for ways to exploit tagclouds.

Yahoo News Tag Cloud:
http://yahoo.theherrens.com/index.php?display=all

This is of interest.

http://lorelle.wordpress.com/2005/10/14/a-tagging-bookmarklet-for-wordpress-and-wordpresscom-users/

btl