This is a full-featured Augmented & Alternative Communication solution for $189.99. While this seems pricey, it is significantly less expensive than other AAC devices.
This is the app version of the Mac program and offers a comprehensive solution for diagraming, charting, designing pages, creating wireframes, and more. It is expensive, $49.99, but full of features.
For those looking to create ePubs for students to use on mobile devices, Wappwolf is a great solution. Connect Wappwolf to your Dropbox account, upload a file, and run an action to convert it.
This free app creates a private diary that stays completely on iPad. For elementary students without the ability to create accounts, this could be a good solution. Notes can be exported via email.