A super nice member!
I use Prezi to deliver short lessons and I encourage students to use it as an alternative to PowerPoint. Over the last year or so it has gained more functionality and ease of use. Students spend one hour getting the gist of it and then they're producing amazing presentations. I like the fact that work is automatically saved to the cloud, students can collaborate on presentations easily, and work can be shared virtually anywhere.
If you're a teacher, you can get a free 500mb account that allows you to keep presentations private instead of the default public setting.