Delicious

Delicious is a service of social bookmarking web. Allows you to add markers that typically were kept in browsers and categorize a labeling system called folksonomies (tags). Not only can store websites, but also allows sharing with other users of del.icio.us and how many have saved a particular link in your bookmarks.

One of the secrets of his success is perhaps the simplicity of its interface, using very simple HTML and a set of readable URLs. It also has a flexible web syndication service through RSS and an API that allows applications to work quickly to del.icio.us.