This is a great article from UX Magazine. It does a great job defining interactivity and gives video examples of eBooks and eBook apps that have value.
With Ebook Glue, add your blog's RSS feed and instantly convert it to an eBook file that can be downloaded and then edited with some eBook creation apps. This could be a great tool for students to use when curating their own blog posts at the end of the year.
This is an interesting take on eBooks for pre-school children. Though not free, the app includes audio books, games, and the ability to send a custom report on the students' progress.
This free eBook is available for download and provides a great interactive resources. Each section ties into some aspect of Bloom's Taxonomy and provides additional information to support iPad integration into the curriculum.
Touted as "the simplest way to make your own interactive eBook" this free program works on both Windows and Mac computers and is a great alternative to Apple's newly released iBooks Author.
This app allows you to have full text-to-speech capabilities with eBooks on your iPad. Any book in the public domain can be read and listened to in one app.