Wikis

BookStack: An open-source platform that allows users to create, organize, and manage wikis in a straightforward way. It’s perfect for those seeking a clean, modern aesthetic.
DokuWiki: DokuWiki is a standards-compliant, easy-to-use wiki that accepts plain text files and requires no database.
Foswiki: Foswiki is a flexible, robust platform enabling users to create and maintain content collaboratively.
MediaWiki: MediaWiki is a free, open-source software developed by the Wikimedia Foundation. It powers all of Wikipedia’s sister projects.
PmWiki: PmWiki is a wiki-based system for collaborative content creation and maintenance with an easy-to-understand syntax.
Scribbleton: Scribbleton offers an easy-to-use, personal wiki that allows you to create interconnected information seamlessly.
TiddlyWiki: TiddlyWiki is a unique, non-linear notebook for capturing, organizing, and sharing complex information.
Tiki Wiki: Tiki Wiki is a powerful, feature-rich, open-source wiki engine that allows users to create and manage various types of content.
~~Torchpad~~: Torchpad offers real-time, collaborative wiki editing powered by Markdown.
TWiki: TWiki is a flexible, powerful, and easy-to-use enterprise wiki, enterprise collaboration platform, and web application platform.
Wikia: Wikia, also known as Fandom, is a wiki hosting service that offers a robust platform for fan communities.
Wikidot: Wikidot is a comprehensive, high-quality wiki platform emphasizing ease of use and flexibility.
wikidPad: wikidPad is a Wiki-like notebook for storing your thoughts, ideas, and to-do lists in a structured manner.
XWiki: XWiki is a free, open-source wiki software platform that is written in Java. It offers a variety of features, including a WYSIWYG editor, OpenDocument-based document import/export, semantic annotations and tagging, and advanced permissions management.
Zim: Zim is a graphical text editor used to maintain a collection of wiki pages. Each page can contain links to other pages, simple formatting, and images.