Prezi is a presentation tool that allows you to create concept maps and notes on a single canvas. You can zoom in and out, create frames for emphasis, resize text, doodle, and map paths to create a slideshow. Think tag cloud on steroids as one analogy.
I'm sure that it would work great in an English, Social Studies, Science (minus chemistry equations), or other general elective class, but using it for math notes is a big chore. Writing in the presentation is easy enough, but you cannot permanently group the numbers together (as is a snap in SMART Notebook), which makes resizing written text next to impossible.
So, all told, it took me about 2 hrs to create this. To best understand a Prezi, check out mine.
It probably goes without saying, but my Prezi does not nearly capture the potential for the tool. Much better examples and ideas exist on their website.
Math use: Unless I get dramatically faster at creating these notes, Prezi's practicality is nearly nonexistent when compared to just jotting notes in my IWB software. The extra pizazz could be worth it occasionally, however. One thing I really like is the ability to embed my Prezi into this blog or an assignment on our district's class website/news service, Edline.