SlideShark is a very good presentation app. As a teacher, you will find several powerful features in SlideShark to use in your own instructional presentations in class. SlideShark enables you to present and share your powerPoint presentations and PDFs from your iOS devices (iPad, iPhone or iPod). You can also easily import presentations stored in cloud storage providers such as OneDrive, Dropbox, or Box, and use them on SlideShark.
http://www.educatorstechnology.com/2015/12/here-is-another-great-presentation-app.html