Prezi is not your mom's presentation tool! Prezi does not just create linear presentations, but it also allows you to create a path between the information that you create, linking it in any order that you want. Zoom into the information for details, or zoom out for a global view of the presentation.
Link to a very quick prezi presentation that I made: http://prezi.com/64909/
I signed up for a free account, which does not offer me an option to make my presentations private. However, there are paid subscriptions available that has this feature. My free account comes with 100 Mb of storage. This is a great tool if you have key ideas or pictures that you want to focus in on quickly instead of having lots of text on a screen.