WikiMatrix - Compare them all
ScrewTurn Wiki is a fast, powerful and simple ASP.NET wiki engine.
FlexWiki Windows + IIS wiki
PhpWiki a clone of the original WikiWikiWeb
Canvas ColdFusion Wiki
Quickie is a small footprint, fast C++ Wiki engine. License: GNU GPL.
DokuWiki is a standards compliant, simple to use Wiki, mainly aimed at creating documentation of any kind. It is targeted at developer teams, workgroups and small companies. It has a simple but powerful syntax which makes sure the datafiles remain readable outside the Wiki and eases the creation of structured texts. All data is stored in plain text files – no database is required. Language: PHP. License: GNU GPL.
PmWiki Language: PHP. License: GNU GPL.
CiWiki Language: C. License: GNU GPL v3.