Technorati.com is a search site that indexes blogs – Google for blogs, as I’m sure Technorati doesn’t like it put. It also lets you embed a chart of how frequently a word is mentioned on blogs over time. This one charts the occurence of tags, tagging and folksonomy:

Posts that contain Tags Tagging Folksonomy per day for the last 30 days.

Click here to get your own chart.

(Disclosure: I’m on Technorati’s advisory board.)