I recently attended a conference called the Summer Institute of Distance Learning and Instructional Technology (SIDLIT…pronounced Side Light). In years gone by I have been a fan of using clickers in the classroom as a way to engage and assess students, but you have to have the devices and they cost money. Enter Plickers or paper clickers. Plickers work with a free app on your iPhone or Android smart phone. Print the cards, hand them out to students and then display your question to the class. Students hold up the paper card with the letter of their answer on top. I was student #18 and I answered C in the image below. Then, the instructor walks around the class scanning the cards. This works best with a small group and goes quite fast. Real-time results are displayed to the class.
Find more information here: https://www.plickers.com/