Social bookmarking tools - Teaching Hacks:
"What is Social Bookmarking
There have been many different attempts to classify web sites through the use of more traditional classification systems such as Gail Shea Grainger's 'Dewey Browse.' Dewey Browse uses the Dewey Decimal System to classify web sites for grades K-12 students. The problem is that web sites come in and out of existence. Other commercial ventures offer a more up to date list of web sites for students and teachers at a monthly price. A few examples are 'StudentLink' and 'NetTrekker.'
All these services, free or commercial, use a top down approach for organizing web sites into predefined categories. Where individuals might make suggestions through a submission form on categories or web sites, but have very little effect the organizational structure of the web site.
Social bookmarking sites turns the hierarchical model upside down. In the past an individual might have saved their favourites or bookmarks on their local computer. Their bookmarks might have been organized under a few general headings. The social bookmarking web site allows individuals to store their bookmarks on the Internet and makes them accessible anywhere."