Social Bookmarking
Social bookmarking is a method for Internet users to organize, store, manage and search for bookmarks of resources online. Unlike file sharing, the resources themselves aren't shared, merely bookmarks that reference them.
Top Social Bookmarking List
http://www.twitter.com
digg
http://www.digg.com
StumbleUpon
http://www.stumbleupon.com
http://www.reddit.com
clipmarks
http://www.clipmarks.com
Delicious
https://delicious.com/
Diigo
http://www.diigo.com
MyBookmarks
http://www.mybookmarks.com
Squidoo
http://www.squidoo.com
Technorati
http://www.technorati.com
Yahoo! Bookmarks
http://beta.bookmarks.yahoo.com