Perl
CGI::pWiki, CGI::Wiki, Chiq_Chaq, Kwiki, PageMate by Furnival Design, TMNetWiki, TWiki.org, UseModWiki
PHP
Elaborate wiki engine, MediaWiki, net.nemein.wiki, PHPWiki, PmWiki, roWiki, sfWiki -- a Wiki for SourceForge sites, Tiki, Wacko Wiki, Wikepage
AfpWiki
Open Source wiki engine programmed with Active FoxPro Pages. It is able to use Visual FoxPro and SQL Server databases.
coWiki
A content management tool with an intuitive markup language, unixlike access management, a directory structure and seamless page renaming.
FlexWiki
A wiki implementation that uses Microsoft's .NET technology (C# and ASP.NET) and has support for wiki namespaces.
GeboGebo - Wiki system
GeboGebo is an open source wiki system based on tdbengine. It is small, easy to set up and administrate and stores all data in a local, indexed database. It can optionally hold all content as static html pages, too.
Perspective
Open Source wiki engine, written in C#/XSLT, that supports WYSIWYG editing, file attachments, searching across pages and attachments (including MS Office documents) and a flexible security model.
Platypus Wiki
A Semantic WikiWikiWeb that uses RDF to manage metadata and ontologies.
RWiki
A Japanese WikiClone built using dRuby, ERb, RDtool, MutexM; inspired by Tiki.
SushiWiki
A wiki-like Web application running on .NET platforms. It is written in C#, uses ASP.NET features and stores data in SQL databases or flat XML files.
Swiki Swiki
Squeak-based implementation, with information about the code and about other Swikis (Squeak Wikis).
TiddlyWiki
An experimental microcontent WikiWikiWeb built by Jeremy Ruston. It's written in HTML and JavaScript to run on any browser without needing any serverside logic. It allows anyone to create self-contained hypertext documents that can be posted to any web server, or sent by email.
Vanilla
An extensible wiki engine written in REBOL, with weblog features and a streamlined interface.
Wiki Engines
Links to dozens of Wiki system types, in many programming languages.
WikiWeb, Inc.
Commercial Windows-based implementation written in Smalltalk with limits on allowed named users, Access support, and ODBC support with more expensive versions.