Explain Everything is one of the most versatile, powerful apps that I have used in the classroom setting. Check out the website for Explain Everything at www.explaineverthing.com.
I like this simple tutorial showing the basic features of Explain Everything: http://www.youtube.com/watch?v=WdzTSeRYkwg
You can add photos from your camera roll and edit the photos in a very creative way. Watch this video for some amazing tips: http://vimeo.com/76894396
Here is a first grade Explain Everything video about the Life Cycle of Butterflies
One more resource for you to refer to is this website of video tutorials at morriscooke.com