SurveyMonkey. I guess lots of people have heard or even used it. Just right now I made my first survey there, a questionnaire about an advanced R course I will hold in DKFZ. I recommend it to everybody who need a (not necessarily small) survey and do not want to do everthing from scratch.
The tool is designed very clean. Common types of questions (multiple choice, matrix of choices, text boxes, etc.) are all at hand and easy to use. Free version allows no more than 10 minutes and less than 100 participants, which is quite fine for my purpose. The experience with the tool was really comfortable. I should definite learn something from their design.
Enjoy your own questionnaire with it!