In-class poll/survey on iPad/iPhone/laptop

If you want to take a quick pulse/poll/survey/quiz in class, there is a nice app for that: Socrative. For iPad/iPhone, there is a student version (iTunes link) and a teacher version (iTunes link). Both are free. You can also use Socrative on your laptop via a browser. A teacher creates an "activity" consisting of question(s) for which students provide responses. The teacher can choose between free-form responses or multiple choice. The teacher needs to register (email and password), but the students do not.