Survey Monkey works pretty well, and you don't have to pay for it, only if you want the bells & whistles. Another I heard about was doodle.com, but I don't know if it has a free component.
Lakeland Public Library, Lakeland, Florida
There's also zoomerang, but we've compared it to Survey Monkey and Survey Monkey seems much better.
I've only used doodle.com to set up meetings. You can fill in dates and times you are available and send out a request to everyone else who is invited. Each person then can select which of those dates and times they could make a meeting. Then you can figure out when most ppl are available. Works really great and it is free. But, I don't think you could do just a general survey with it.