Socrative allows students to respond to questions.  Teachers set up questions and then have students answer those questions in real time using any smartphone, tablet, or computer.  Questions can be set up to assess by true/false, multiple choice, or even short answer.  Setting up a quiz with Socrative is very simple and each quiz is auto corrected which create more time.  Socrative has apps/log-ins for the teacher and students.  One of the best features of this whole program is that its all FREE!  The video embedded below explains more about Socrative.