Social Bookmarking is basically a fancy way to bookmark websites. Users can share, organize and manage bookmarks. The first thing you do is give each bookmark a tag. You can also put them into folders as well. Then you can share your bookmarks, tags, etc. with others.
There are pros and cons to tag-based bookmarking. However, for most users it provides a way to organize and share bookmarks. Some of the social networking bookmarking services include:
Delicious, Ma.gnolia, Faves, Diigo, Connectbeam