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
Product Pains - Giving users a louder voice to help teams build better products.
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.
Nolt - A fast & beautiful way to collect user feedback
Survicate - Collect feedback on your website and find out more about your visitors.
idea.informer - Idea Informer is a idea forum similar to uservoice or getsatisfaction.