9Slides is an excellent site/app that I've blogged about in the past. This is a great tool for adding video/voice narrations to all kinds of presentations (ie, PPT, Keynote, etc). This is ideal for Guided Learning as well as "flipping" a classroom. With 9Slides new educational portal educators can create and share educational content, track student usage, and more.
I highly recommend checking out 9Slides by clicking here!!!