I've added a new drupal module called tagadelic to this site. It takes category tags associated with postings and creates a representation of the popularity of each tag. The more popular a tag the bigger and bolder it gets.

It has meant that I've had to go through and re-tag all of the content on the site. I've done about a year's worth so far; it's something for those quieter moments. Recent versions of Drupal's category module has a 'free-tagging' mode that allows you to create new tags on the fly rather than having to pre-define them as was the case previously. Categories can be further defined, adding hierarchical relationships and creating synonym relationships.