Though not free, this assessment app includes the ability to easily capture photos and video into a rubric and then upload to DropBox. Could be great for administrators.
Technology Integration Matrix with video examples for every topic and level of integration. Not iPad specific, but a great place to start when integrating technology.
Vernier offers a host of products to support physics instruction, and for $2.99 there is now an app. Students can perform hands-on experiments and collect real-time data through the iPad.
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.
This site offers tools for studying vocabulary. There is also a selection of apps available. What makes this interesting for students is the visuals provided by both images as well as video to give additional cues for learning words.
This is an interesting app that seems to be a cross between Fotobabble and Animoto. The idea is that you can record ambient sound while taking pictures in order to create a short video. Could be an interesting way to document field trips or create a digital story.