The personal computer is credited for the demise of the encyclopaedia salesman - instead of spending hundreds or thousands of dollars on an encyclopaedia set, you could buy a product like Microsoft Encarta on CD-ROM, and have not only text but video and audio content as well. With the advent of the internet there is a new way to access information, however, unlike a book or a CD-ROM, there are quality and trust issues with using Google or another search engine to research answers.
In early 2000, Jimmy Wales and Larry Sanger decided to create an innovative online encyclopaedia, one that would invite people to make contributions and edit the pages of the encyclopaedia themselves, sharing their knowledge and expertise with the world. The result some 5 years later is Wikipedia, a living, online encyclopaedia in more than 50 languages, with more than 10,000 contributors maintaining over a million documents.
The English section of Wikipedia - http://en.wikipedia.org/ - has around 500,000 articles on all manner of topics. Because it is maintained by many of the people who visit the site, it is also tremendously responsive - during the Tsunami crisis over the holiday period, Wikipedia was by far the most accurate, detailed and authoritative news source on the disaster, including animations, explainations for how Tsunamis happen and a lot more.
The joint winner of the 2004 United Nations award for digital communities, Wikipedia is built around open-source philosophies. Contributors to the site volunteer their time and information when they edit pages, and anything posted to the Wikipedia site is provided under the terms of the GNU Free Documentation Licence, where the author retains the ownership of the information they provide, but allow others to copy, modify and redistribute that information without limits.
Wikipedia also has a number of sister sites, including Wikiquote, a library of quotations; Wikibooks, a collection of free and open text-books; and Wikisource, a repository of copyright free books and speeches (including the Bible, Qur'an, Communist Manifesto, etc).
Wikipedia Internetrix Article: http://en.wikipedia.org/wiki/Internetrix