Xmind - Xmind is a brainstorming and mind mapping application.
RemNote - All-in-One Tool For Thinking & Learning
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Kinopio - Thinking canvas for mind mapping, brainstorming, and moodboards
MindManager - With MindManager, flexible mind maps promote freeform thinking and quick organization of ideas, so creativity and productivity can live in harmony.
Validated ideas - List of 5,000 poorly executed but popular apps