Keynote for iPad is a staple in schools with iPad programs. Students are presenting to the class more and more with projects created all from an iPad. One great feature of keynote is its ability to embed video in a slide and at the end of the video, transition to the next slide. It just makes your presentation so much smoother and can make the whole thing play without any interaction. This is useful for getting everything in with a given amount of time or looping the presentation at your baking soda volcano exhibit. On keynote for mac you get 600 seconds to allow for this, on an iPad you get just 60.
Well with a little creative thinking, you can make this much longer.