Prezi

A quick mention for Prezi, an online presentation tool that's based on zooming in and out on text and pictures.

Describing it doesn't really do it justice. I've played with this tool for a bit and, although there's an art to it that I don't really have as of yet, these presentations can be very effective. I like this Prezi that discusses the concept of these presentations and how to best deliver them.

There are free and fee-based versions, detailed here. The differences are in the amount of disk space online, privatizing content, removing the Prezi watermark and the use of an offline desktop presentation development tool. As a teacher, you could use start with the free version and could allow students to do the same. I would recommend viewing a few sample presentations, as users are aching for something that catches the eye a bit more than the standard presentation. This tool can be very effective to zoom in on ideas, walk across timelines, create online flowcharts, etc. It's definitely worth a try!