Nifty - Manage projects, work, and communications in one place.
Xmind - Xmind is a brainstorming and mind mapping application.
Intercom on Product Management - The ultimate resource for aspiring product managers
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
productboard - Beautiful and powerful product management.
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.