I have been having a play around with some photo Apps. I was thinking if you were doing a unit on cultures around the world and looking at food, famous places, etc. how much fun would it be to superimpose photos of the students in these places. These photos could then be used in Keynote, iMovie, Book Creator etc. as part of a research project. Then I thought, what about going one step further and making a video from this photo using iFunFace. They could do a news report or David Attenborough type documentary. The videos could then be put into one of those apps or what about a collaborative class book, presentation or movie with everyone in the class having a page. There are a few free apps that you can use to do this. They do tend to have advertising as they are free. I found some by googling it first. I won't recommend one because they had different features depending on what you want.
Link here to watch a very quickly put together version.