For posterity, some lame php code made when tags were brand new and web2.0 was all the rage: Analys.icio.us allow you to draw a map of words. The bigger are the most used. You can analyse plain text or an url. There is no meaning in the word position. If you move your mouse over a word, you’ll get a tooltip with the word count. You can download the code.
Word Popularity Colorizer: Colorize words of an url
Wordcount: Artistic experiment in the way we use language
extisp.icio.us: Same kind of map but for del.icio.us tag
WordPress Category Map: Same kind of map but for wordpress category