Survicate - Collect feedback on your website and find out more about your visitors.
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.
Survey Monkey - Create and publish online surveys in minutes, and view results graphically and in real time. SurveyMonkey provides free online questionnaire and survey software.
KISSinsights - Give customers a way to tell you what they need. Get real-time feedback from your customers on your website, free.
SurveyJS - Feature rich and open source surveys for embedding into websites.
Zync Free Surveys - Free survey, quiz and e-learning, web iOS & android app.