MediaWiki - Used by tens of thousands of websites and thousands of companies and organizations. It powers Wikipedia as well

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Meta-Wiki - The global community site for the Wikimedia Foundation's projects and related projects, from coordination and documentation to planning and analysis

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Wikibooks - Open-content textbooks collection that anyone can edit

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Wikidata - The free knowledge base with almost 90 million data items that anyone can edit

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Wikimedia Commons - A collection of 64,133,442 freely usable media files to which anyone can contribute

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Wikimania - The official annual conference of the Wikimedia Foundation

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Wikinews - The free news source you can write

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Wikiquote - The free quote compendium that anyone can edit

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Wikisource - The free library that anyone can improve

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Wikispecies - The free species directory that anyone can edit

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Wikiversity - Project devoted to learning resources, learning projects, and research for use in all levels, types, and styles of education from pre-school to university, including professional training and informal learning

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Wikivoyage - The free worldwide travel guide that you can edit

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Wiktionary - A collaborative project to produce a free-content multilingual dictionary

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Wikipedia - Find more than 6,000,000 English entries, written and edited by users

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