Important Notice We are making some changes to the Term Extraction Web Service: The service will be only accessible via YQL.
You've seen it for the first time (as far as I know) on Flickr and you're seeing it on major websites as well. The "tag cloud" or "weighted words list" is nothing more than another way of displaying a navigation. It's funny, weird, new to the internet, attracts clicks, easy to do and it's also free. It's so easy to do a tag cloud using this simple PHP functions that I've found.