There's quite a buzz now around so-called "tagging sites." The easiest way to describe tagging sites is that they are essentially a Web-based version of the favorites list on your Web browser. Users post their favorite Web sites and Web pages to these tagging sites, which then makes them generally available, or only to a group specified by the user.

In their original incarnation, tagging sites were more of a novelty and convenience than any great breakthrough. But they've been quietly evolving, adding more features and functionality, and as a result are becoming more popular and important as information discovery tools.

Sites such as kaboodle.com, reddit.com and shadows.com, all offer different flavors of the tagging experience, but the common elements are individuals selecting, classifying and sharing interesting Web destinations. In another twist, a Web site called wink.com has now created a search engine that indexes these tagging sites, attempting to improve upon Google's relevance rankings by limiting itself to these recommended pages and sites.While tagging seems to live largely in the world of consumers and hobbyists for now, it manifests larger trends that have implications for all of us.First, that tagging is flourishing is proof of a large and enduring need to organize the Web in order to extract maximum value from it. The Web is simply too vast for anyone to expect that, with a simple search engine query, they will get to the best information resources quickly and easily, if at all. Just as importantly, it's not always obvious that you've found an outstanding Web resource even if you do stumble across it, because the big searches are focused on relevance, which is a weak proxy for quality. Tagging is an attempt to overcome some of these limitations of the big search engines.

Second, while the models vary a bit, tagging isn't really about users classifying the Web content they find, it's much more about the new "3R's" -- ratings, ranking and recommendations. Tagging essentially layers a voting system on top of full text search to (hopefully) present even more precise and valuable search results.

Third, tagging reinforces the notion that true community, in the form of an information commons, is taking root on the Web. In this case, all the recommended Web pages are contributed to a common pool, and the community then works in a collaborative fashion to assess and rate these contributions.

Finally, the tagging craze offers more support for my contention that search is beginning to fragment. While current tagging sites for the most part suffer from trying to be overly inclusive, it is clear that tagging has the most power and value in vertical search-style applications, where a community of experts contributes to a pool of content that is then rated by other experts, assuring that the best available content is recognized and becomes readily accessible.