PowerPoint has become the default visual presentation program in classrooms across North America. If a teacher has a Mac in their classroom they may have used an Apple program called Keynote to present their material. Keynote is by far the best presentation program available today, but it is only available on the Mac.
The developers of Keynote decided to break away from Apple and open their product to the rest of the world (Pcs). Enter 280slides.com. 280slides is almost identical to Apple's version except is has one advantage, it is avialable to anyone with an Internet browser. And best yet, it stores your presentation in the cloud (Internet) so you don't have to worry about forgetting to bring your usb drive to class.
280slides offers a free limited version, and a paid version that offers more features and storage.