If you haven't used Explain Everything yet, it is a fantastic app for the iPad or iPod (and also Android devices) that allows you to create presentations, or even use it as a digital whiteboard. I use it all the time in my class, with my iPad mirrored wirelessly to my projector (via AirServer). It has a lot of amazing features, many of which I am still learning about.

I found this great tutorial, found here, that walks you through some great features, like how to group and arrange objects, putting a web browser in your screen and annotating on it, and exporting to a variety of devices and applications.