ClearFlask - Open-source Product Feedback Tool with a Public Roadmap and Announcements.
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.
Fider - Fider is an open source, cross platform and free to use customer feedback platform for companies...
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
Nolt - A fast & beautiful way to collect user feedback
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.