Idea Hunt - Solve specific challenges for your favorite products
Xmind - Xmind is a brainstorming and mind mapping application.
Flopstarter - A platform for bad ideas
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
IDEATOSHARE - Idea sharing community
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.