NearPod is a free service/app that allows you to create interactive lessons and then share them across iPads in your classroom. Teachers create interactive presentations and then share them with the class.
Here's how it works. The teacher uses the Content Tool to create multimedia presentations and then share the content with the students. The Teacher app allows the teacher to control the activity also. Students receive content and assessments on their device and then can submit answers and responses. The teacher can use the Reporting tool to monitor what the students are doing and collect their responses, assess their learning and gather data.
The multimedia presentations start with a PDF file and then quizzes, polls, videos, activities and more can be added.
It's free, easy to use, and a great resource to use with iPads in the classroom.
Get it from the App Store: http://itunes.com/apps/panarea