Xmind - Xmind is a brainstorming and mind mapping application.
DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Wiki.js - An open source, modern and powerful wiki app built on Node.js, Git, and Markdown.
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.
TiddlyWiki - a non-linear personal web notebook