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.
SlimWiki - Beautiful Wikis for Teams. Get started today, free forever!
Linkpack - Save, read and share your links
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
Pocket - When you find something you want to view later, put it in Pocket.