Explain Everything is an easy-to-use design tool that lets you annotate, animate, and narrate explanations and presentations. You can create dynamic interactive lessons, activities, assessments, and tutorials using Explain Everything's flexible and integrated design. Use Explain Everything as an interactive whiteboard using the iPad2 video display.
This site is similar to the Khan Academy, except the video tutorials are made and contributed by a wide variety of individuals. As a result, the quality (and credibility) of some of the videos is questionable, but there are still some useful videos here.