Prezi.com has free accounts, some specifically for educators, which allow you to use their web-based interface to create amazingly attractive presentation that can be saved online and to your computer.
The arrangement of ideas are linked on a large “playing field” with a path that you create by selecting ideas in the order you want them presented. Prezi automatically tracks the path with proper movement and zooming, depending on the size and placement of the idea and allows for sequanetial advancement with arrow keys or the presenter can “click around” intuitively.
Here is a simple tutorial that will get you started in 5 minutes.
Here is a Prezi that explains how to use Prezi!