Let's talk about games. Educational games. Students love the idea that they get to “play games” on their iPads, and teachers love to subversively teach students important concepts in a fun way. The app store is filled with a great collection of educational games (many aimed at younger students), and our school is totally okay with students installing and utilizing them during free time, between classes, or after school.
Currently, two of the most popular are Stack the States ($0.99) and Stack the Countries ($1.99). The students love these games. A lot. Even kids as young as seven (2nd grade) are really, really into them.
It is important to remember that utilizing an iPad in the classroom need not require every student to have an iPad with some expensive app and a complicated lesson plan that you spent hours developing that utilizes the app in unique and interesting ways. That is great to do, of course, but one of the more straightforward uses of an iPad is to take the ordinary elements of a classroom and make them extraordinary.
To replace the standard roll-down map at the front of the classroom, we have Google Earth instead. All you need is one iPad, the free app, and the ability to mirror your screen using an AppleTV or AirServer.