LimeSurvey – Leading Open Source Tool for Online Surveys
http://www.limesurvey.org/

LimeSurvey basically contains everything you need for doing nearly every survey with grace. What is still missing will most likely be found in their rapidly shrinking roadmap. Features include:

*Unlimited number of surveys at the same time
*Creation of a printable survey version
*Unlimited number of question groups in a survey
*Unlimited numbers of questions in a group/survey
*20 different question types with more to come
*Ability to set conditions for questions depending on earlier answers (branching the survey)
*Re-usable editable answer sets
*Ready-made importable questions
*Assessment surveys
*Unlimited number of participants to a survey
*Anonymous or open surveys as well as closed surveys
*Optional public registration for surveys
*Sending of invitations, reminders and tokens by email
*Option for participants to buffer answers to continue survey at a later time
*Cookie or session based surveys
*Template editor for creating your own page layout
*Extended and user-friendly administration interface
*Back-office data entry possibility
*Survey start & end-dates for automation
*Enhanced import and export functions to text, CSV and MS Excel format
*Basic statistical and graphical analysis with export facility
*Supporting more than 20 different languages in frontend and backend

This has been added to the tools section of Research Resources Subject Tracer&trade’ Information Blog.