Social information processing is "an activity through which collective human actions organize knowledge." It is the creation and processing of information by a group of people. As an academic field Social Information Processing studies the information processing power of networked social systems.
Typically computer tools are used such as:

Authoring tools: e.g., blogs
Collaboration tools: e.g., wikis, in particular, e.g., Wikipedia
Translating tools: Duolingo, reCAPTCHA
Tagging systems (social bookmarking): e.g., del.icio.us, Flickr, CiteULike
Social networking: e.g., Facebook, MySpace, Essembly
Collaborative filtering: e.g., Digg, the Amazon Product Recommendation System, Yahoo! Answers, Urtak
Although computers are often used to facilitate networking and collaboration, they are not required. For example the Trictionary in 1982 was entirely paper and pen based, relying on neighborhood social networks and libraries. The creation of the Oxford English Dictionary in the 19th century was done largely with the help of anonymous volunteers organized by help wanted ads in newspapers and slips of paper sent through the postal mail.