Wikipedia is a free, collaborative encyclopedia written in 300 languages by volunteers around the world.

Wikibooks aims to build a collection of free e-book resources including textbooks, annotated texts, instructional guides, and manuals.

Wiktionary is a free multilingual dictionary. The project aims to describe all words of all languages. It includes language resources such as a thesaurus, rhyme guide, and language statistics.

Wikiquote is a online collection of sourced quotations from notable people and creative works in over 75 languages. It also includes proverbs, mnemonics and slogans.

Wikimedia Commons is the world’s largest free-to-use library of illustrations, photos, drawings, videos, and music.

Wikisource is a library of freely-licensed source texts and historical documents, including poetry, government documents, constitutions of many countries, and general literature.

Wikiversity is devoted to learning resources, learning projects, and research for use in all levels, types, and styles of education.

Wikispecies is a species database for taxonomy that covers living and fossil representatives of Animalia, Plantae, Fungi, Bacteria, Archaea, Protista and all other forms of life.

Wikidata acts as central storage of structured data for Wikimedia projects. Structuring data into a machine-readable format makes it easier to view, search, edit, curate, use and re-use files.

MediaWiki is free and open source wiki software that anyone can use and develop. It is the platform on which Wikimedia projects are built.

Wikivoyage aims to create the world's largest free, complete and up-to-date worldwide travel guide.

Wikinews provides a free content alternative to commercial news sites with articles that are fact-checked and peer reviewed.

Meta-Wiki is a project used as a central hub for various coordination and organization tasks, such as discussions affecting multiple wikis or planning upcoming events.