Social bookmarking is an increasingly popular way to locate, classify, rank, and share Internet resources through the use of shared lists of user-created Internet bookmark, the practice of tagging, and inferences drawn from grouping and use of such tags. In such a system, users store lists of personally interesting internet resources, and (usually) make these lists publicly accessible. They also classify their resources by the use of informally assigned, user-defined keywords or tags. Most social bookmarking services allow users to search for bookmarks which are associated with given "tags", and rank the resources by the number of users which have bookmarked them. Click here for the Common Craft explanation of Social Bookmarking. This video will be blocked by the Bess proxy.
7 Things You Should Know About Social Bookmarking (pdf)
Social Bookmarking in Plain English
Backflip
Blinklist
Diigo
Portaportal
Simpy
StumbleUpon