Xmind - Xmind is a brainstorming and mind mapping application.
UserVoice - UserVoice integrates easy-to-use feedback, helpdesk, and knowledge base management tools in one platform that empowers users to speak and companies to understand.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.