SoGoSurvey is the best service of it's kind, in my opinion. They have a number of tools through their site that allow for a high degree of customization. Very happy with this aspect this company.
However, I am VERY unhappy over the fact that I have been receiving endless emails and phonecalls from this company on a daily basis. Following up is understandable, but give me a break. Let me explore the basic/free package for a couple of weeks at least before you start aggressively trying to upsell me.