[Air-l] Online survey tools

I have to do an online survey to gather ethnographic data for a research paper. I know of a few survey tools out there that are completely hosted and provide an aggregate of the results, but I've no idea what their cost is. Have any of you used some good tools for this? I basically want to be able to send my prospective respondents a link via email that they follow to fill out the survey online and submit it. It would be approximately 20 questions, with only a few allowing write-in responses. Ideally I'd like to export the results afterwards into a spreadsheet for analysis and crunching. Tamara