Scapple - Scapple is an easy-to-use tool for getting ideas down as quickly as possible and making connections...
vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
Visual Understanding Environment - Visual Understanding Environment (VUE) is a mind-mapping and concept-mapping tool.
Xmind - Xmind is a brainstorming and mind mapping application.