StoryKit is a free iPhone/iTouch/iPad app from the International Children's Digital Library. It allows the user to create story books using multimedia including images and audio clips. Integrated into the program is a paint program and ability to share books you make.
You can use this app to create scrapbooks of recent classroom events, social stories and visual schedules. Essentially you are limited only by your creativity.
If you download the free ARASAAC or Scelera Picture Symbol (or the Mayer-Johnson PCS Metafiles or similar) set onto your iDevice you can intergrate picture symbols into your "book". Otherwise you can use photographs you take with the camera (on an iPhone or iPad) or import through iTunes.
StoryKit has the possibility to replace some of the more expensive prompting (a visual schedule could be created with one picture per "page" and audio of what happens next and a child taught to turn the page when done with each step or his helper could do that for him) or storyboard programs, so long as you aren't looking to have an alarm or timer.
StoryKit also has access to the books in the International Children's Digital Library to read and share together.