PollDaddy is a crowd favorite; I've seen lots of folks using it, and no wonder -- it's robust (you can ask multiple choice, short answer, long answer, . . .), it's pretty (you have a number of styles to choose from for the look of your poll or survey), it dovetails nicely with other popular tools such as Blogger, and you can embed a poll in your slide presentations.

My single biggest question when looking at PollDaddy was this: what's the difference between a Poll and a Survey? Looks to me like a Poll is a simple, one-question, multiple choice, immediate feedback type deal (which is why it is so popular to embed it into a slide presentation), whereas the survey can contain as many items as you'd like, in whatever format you would like. These images give you an idea in the visual difference; go to my Blogger site (and scroll to the bottom of the page) to try the poll and the survey for yourself!!