Mentimeter

Mentimeter is a free teacher resource that allows you to survey a group and create real-time data. The teacher poses a question and posts the code for students to use to cast their votes on a cellphone or other wifi-enabled device.

I used it for classroom management at the beginning of the year. I would ask students to list attributes that make a great classmate. I set it up to create a word cloud of their responses and would tell them that this would be our class contract with one another. It is definitely eye-catching for students.

Some downsides to this is that there is no way to tell who gave what response. Also, the free account has a limited number of surveys you can create and save. (A workaround is to delete old surveys when you don't need them.)