Canny - Canny helps you collect and organize feature requests to better understand customer needs and prioritize your roadmap.
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.
Delighted - The fastest and easiest way to gather actionable feedback from your customers
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
Wootric - Wootric is software that allows apps and websites to take customer satisfaction surveys so that you can properly gauge the popularity and success of your app through the eyes of the people using it. Read more about Wootric.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.