According to Wikipedia
Social bookmarking is a method for Internet users to store, organize, search, and manage bookmarks.
In actual fact, it is THE way to catch the latest buzz. Once you decide on a few of these sites and some of the users on these sites, you would be able to discover those hard to find websites and stories that search engines or directories don’t reveal.
For All the Websites You Want to Get Back to We make sure you can find them again!
del.icio.us is a collection of favorites – yours and everyone else’s
Digg is a place for people to discover and share content from anywhere on the web
Drew Curtis’ FARK
a news aggregator and an edited social networking news site, 2000 news submissions daily
a social bookmarking site that makes it easy to save, share, and explore favorite web pages
IndianPad is a social bookmarking and blogging site means that our USERS rule!
access to a human-organized bookmark collection that numbers in the millions
More than 50 Social Bookmarking Sites
Over 500 social networking services that can manage bookmarks for you
a leading social bookmarking service in 6 languages, with over 4 million visitors per month
Online Social Bookmark Manager – Save, Tag and Share your bookmarks
Updated by citizens like you, Newsvine is an instant reflection of what the world is talking
Popular URLs to the latest web buzz
a new social news portal programmed by you the audience by submitting and voting on all stories
reddit is a source for what’s new and popular online. vote on links that you like or dislike
a highly scaleable social search platform that showcases expertise and enables collaboration with peers
a social bookmarking service that lets you save, tag, search and share your bookmarks and more
Slashdot News for nerds, stuff that matters
the free service designed to reduce the time and effort needed to socially bookmark a website
Join 4,550,136 Stumblers & Discover New Sites. Channel surf the Net with StumbleUpon toolbar
a service to communicate through frequent answers to one question: What are you doing?
Yahoo! Buzz features the most popular stories right now, determined by people around the Web. A story’s Buzz Score is based on your votes, searches, emails, and more. Stories with the highest Buzz Score may be displayed on the Yahoo! homepage. Give your favorite stories the buzz!