Flisti is a free online poll website that does not require any sign up. Flisti would be a great tool to use on the first day of school or the beginning of a unit to gauge where students stand on a particular subject. If you teach a current events class Flisti would be a simple way to get a feel for what students are thinking on certain issues. The tool is simple to use. Just type in your question, type in the possible answers, choose whether you want to allow multiple answers, and then click on the "Create Poll" button. You then get a simple URL that you can share and then go back and view later to get results.
If you have a school or class Twitter or Facebook page you can share the poll there as well to get the word out to your students. If students choose too they can log-in using a profile from another service and add comments to the poll, therefore making the poll interactive. If you have students watch the news, you could create polls on news stories and get instant feedback from your students and then discuss in class the next day. Same if you are watching a movie in class as well.
Flisti seems to be a rather simple tool to use and could be easily adapted into the classroom