UseResponse - Open-source, self-hosted customer feedback software, live chat and helpdesk system that you can install on your server. Organize documentation using knowledge base and get feedback from social networks with centralized system
Survicate - Collect feedback on your website and find out more about your visitors.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Helprace - Helprace is a customer service software suite linking a ticket system with help desk software, giving customer support agents a complete helpdesk solution.
Noora - Building the features your users want is not an easy task. With Noora, you can validate your feature ideas and product roadmap before you start development.
hellonext.co - User feedback, feature voting, & roadmap for product management.