Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
iRedMail - A fully fledged, free email server solution, an open source project (GPL v2).
TiddlyWiki - a non-linear personal web notebook
mailcow - An open source mailserver suite.
Confluence - Confluence is content collaboration software that changes how modern teams work