Kahoot! - Create or borrow quizzes, surveys and discussion questions about any topic you would like. Free and very user friendly! Kids can respond on almost any device you have available. Gives instant feedback on students' understanding and/or opinions.
Epic! for Educators - Computer and iPad app that allows kids to read books digitally. FREE for educators. Set up a free educator account and download the app and you are ready to go. Many books will read to the students.