Using an iPad in your classroom? Then you need to be able to project your work on the big screen. First, get a VGA adapter for your iPad, and then start collecting apps that allow VGA output. (Not all apps do this, but that is changing all the time.) See below for some good candidates.
Expedition (a browser)
Note Taker HD
Sundry Notes (it's free)
Penultimate (Good for drawing, formulas, like an overhead)
6Tech Blog article