Bloomfire - Let Bloomfire help you get organized! Organize your content, build your company knowledge base and help your employees to be more successful.
WackoWiki - WackoWiki is a light and easy to install multilingual Wiki-engine.
Confluence - Confluence is content collaboration software that changes how modern teams work
MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
Tettra - Tettra is a company wiki that helps teams manage and share organizational knowledge.
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.