MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
TiddlyWiki - a non-linear personal web notebook
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.
Confluence - Confluence is content collaboration software that changes how modern teams work
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .