Delicious.com

Delicious (formerly del.icio.us ) is a social bookmarking Web service for storing, sharing, and discovering bookmarks. The site was founded by Joshua Schachter in 2003 and acquired by Yahoo! in 2005. By the end of 2008, the service claimed more than 5.3 million users and 180 million unique bookmarked URLs. The site was sold to AVOS Systems on April 27, 2011 and relaunched in a back to beta state on September 27 that year.

Input: 

Primary - 1. Web site links, submitted either directly via the web site or through browser Bookmarklets.
Secondary - Each link submitted can be annotated with a textual description and a set of tags.  Delicious pioneered work with folksonomies with their interface that suggested tags based on heursitics similarity to others’ bookmarks

Human Computation Elements: 

Humans bookmark, categorize and

Mediative Elements: 

Easy bookmarking (Through bookmarklets)
Tag suggestion (via ta gprediction algorithm)

Category type: 
Knowledge Sharing Social Machines