I subscribe to a blog called Class Tech Tips and although not every email I receive has a golden nugget of information in it, more often than not, there is a precious piece of info that makes the subscription worthwhile.
The most recent nugget from Monica at Class Tech Tips was about seven free AND engaging presentation apps for teachers.
She does have Prezi and Haiku Deck on her list – I am not a big fan of either app. And, I would add Googe Slides to the list because of the opportunities for collaboration that come with Slides.