Social bookmarking is a method for Internet users to store, organize, search, and manage bookmarks of web pages on the Internet with the help of metadata, typically in the form of tags that collectively and/or collaboratively become a folksonomy. Folksonomy is also called social tagging, "the process by which many users add metadata in the form of keywords to shared content".
In a social bookmarking system, users save links to web pages that they want to remember and/or share. These bookmarks are usually public, and can be saved privately, shared only with specified people or groups, shared only inside certain networks, or another combination of public and private domains. The allowed people can usually view these bookmarks chronologically, by category or tags, or via a search engine.
Most social bookmark services encourage users to organize their bookmarks with informal tags instead of the traditional browser-based system of folders, although some services feature categories/folders or a combination of folders and tags. They also enable viewing bookmarks associated with a chosen tag, and include information about the number of users who have bookmarked them. Some social bookmarking services also draw inferences from the relationship of tags to create clusters of tags or bookmarks.
Places to social bookmark
Delicious is a social bookmarking service that allows users to tag, save, manage and share web pages from a centralized source. With emphasis on the power of the community, Delicious greatly improves how people discover, remember and share on the Internet.
StumbleUpon is an intelligent browsing tool for sharing and discovering great websites. As you click Stumble!, you'll get high-quality pages matched to your personal preferences. These pages have been explicitly recommended (rated I like it) by friends and other SU members with similar interests. -Video Tour
Diigo (dee'go) is about Social Annotation. By combining social bookmarking, clippings, in situ annotation, tagging, full-text search, easy sharing and interactions, Diigo offers a powerful personal tool and a rich social platform for knowledge users, and in the process, turns the entire web into a writable, participatory and interactive media.