Alternatives to PowerPoint
PowToon
Create animated presentations or videos using their easy to use interface. You can sign in with either your Google account, your Facebook account or your Linkedin account. And your finished videos can be uploaded to YouTube.
Sliderocket
Create a presentation from scratch or import either an existing Google Presentation or Powerpoint. There are a full range of editing tools, and analytics are also built in so that you can track how many views your presentation has recieved. It also works across a range of devices.
Prezi
A web based presentation tool that in places of slides has one large canvas, in which you can select frames. The interface is very easy to use and there are lots of templates to choose from. You can import powerpoint slides, images and videos can be uploaded from your computer or can be taken from the web.