Sarah Perez over at ReadWriteWeb has put together a great roundup of online slide-show tools. One that's not on the list, and instead showed up in the user comments is ZuiPrezi, a not-yet-launched online presentation creator that ditches the idea of individual slides in place of a giant expanse that can be navigated with a mouse, keyboard, and eventually touch screens.
The end result is pretty incredible and feels a lot like Google Maps. It uses vector graphics to keep lines and text nice and clean as you zoom in and out of bits and pieces of a presentation. Media also streams in as you go, so you can begin your presentation from wherever while big photos and videos load in the background.
Microsoft has been experimenting with something similar in its Office Labs program. Called pptPlex, you can use zooming to jump around to different parts of a PowerPoint presentation instead of sticking to a controlled order. ZuiPrezi throws in the added benefit of charting out what order you want the presentation to scroll around in, even if it's all over the map.
The service is still in private beta although there are both preview videos and live examples of presentations to play with. I've embedded the demo video of creating one below, although if you want a thrill you should go check out this lecture from ZuiPrezi founder and designer Adam Somlai-Fischer.