The app that I have used most is iMovie. It is a $4 app, but was worth the money. It offers a variety of intuitive tools to help edit and format your movie. It also has uplaod connections to help get your movie to the patrons you want to see it.
It is also possible to use the iPad camera to record and upload video to YouTube or other social media. Small clips can be emailed, too. I have done a couple movies that wya as well. If you mess up, you have to retake, just like with a real movie.
I will attempt some more movies over the summer and think more about how these could be used in some of the projects that I teach.