Xmind - Xmind is a brainstorming and mind mapping application.
MediaWiki - MediaWiki is a free software wiki package written in PHP, originally for use on Wikipedia.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
TiddlyWiki - a non-linear personal web notebook
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.
Confluence - Confluence is content collaboration software that changes how modern teams work