I've been looking for a way to use photographs and the ipad to help in charting seminar work with students. Kimberly Eggett has hipped me to "Skitch." This app allows me to take a photo (or use an existing photo or web content) and then draw/annotate over it. I'm still working out how these can be shared, but it's a productive first step.
Skitch is free from the App Store.