My 3rd graders are using the Ipad "gem" Kahoot. I set up a game about different genres of books and they would get a clue such as "this genre has smooth writing with rhythm and sometimes rhyme" and they get 4 choices and must choose the correct answer in a game show style. They LOVE this! It is not an app but rather a website but using a tablet is best to choose answers quickly.
Lastly, my 5th and 6th graders are presenting their Big 6 Research book recommendation lists to final publication. Some are using Google docs, slides, a good old poster, and some are using the Ipad app Animoto and creating a video out of images.