This product from the School Improvement Network facilitates administrative classroom walkthroughs in that it leverages the camera capabilities of the iPad/iPhone/iPod Touch and integrates it with assessment tools designed to give teachers constructive feedback.
Though really expensive, this has a lot of potential. Think of it as a presentation tool similar to Prezi. However, the final product can be exported as an Explain Everything project file.
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 an evidence-based app to support speech and occupational therapists as well as special education instructors or parents looking to support their children. It is pricey - $39.99 - but that is less expensive than computer based versions of similar products.
Scribble Press (FREE) is a book creation platform that allows students to both write and illustrate their own stories. Final products can be downloaded to iBooks or ordered as a hard copy.
This is the math app that has been featured in numerous iPad commercials. It is a great product for arithmetic drills and includes problems for addition, subtraction, and multiplication.
Animoby is a sort of screencasting tool, but not really. The idea is to instantly create and publish products that include voice, drawings, and images.