Wikipedia is an encyclopedia which is written entirely by volunteers using a wiki. If you came here and you don't know Wikipedia, please check it out. You'll learn a lot about all kinds of subjects there.
Wikipedia, the biggest open content project ever, also proves that the wiki principle really works in practice to create open content of high and ever-improving quality. The Spanking Art wiki uses the same open source wiki software as Wikipedia, MediaWiki, so everything here works pretty much the same as it does on Wikipedia.
Since it was founded in 2001, Wikipedia users have written over one million articles in hundreds of languages. Wikipedia contains traditional encyclopedia topics as well as almanac or gazetteer style content, with some coverage of current events. But unlike a traditional encyclopedia, It does have issues with reasurch, as while a great place to start looking, should not be treated like an authoritative source, and for this and it's mutable nature, is not normally accepted as a citable source.
Wikipedia is run by the Wikimedia Foundation.