LimeSurvey is the open source online survey tool. LimeSurvey basically contains everything you need for doing nearly every survey with grace. LimeSurvey offers unlimited number of surveys at the same time, unlimited number of question in a survey, unlimited number of participants to a survey, over 20 different question types, multi-lingual surveys, and ability to set conditions for questions depending on earlier answers.
What's new in this version:
Version 200plus-build 130708 adds a function to the expression manager which allows numerical values.