Invision - Prototyping and collaboration for design teams
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.
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.
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
Axure RP - The prototyping and specification software used by 87% of the Fortune 100. Beyond mockups, design interactive prototypes for business solutions, websites, and applications.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.