LimeSurvey (formerly PHPSurveyor) is an open source online survey application. It enables users to develop, publish and collect responses to surveys. Surveys can include branching, custom preferred layout and design (using a web template system), and can provide basic statistical analysis of survey results. Surveys can be public, or can be strictly controlled through the use of "once-only" tokens for each survey participant.
Web Site: http://www.limesurvey.org/