The best solution IMO is to use Open Office, Keynote, PowerPoint etc to build the show and then upload it to a cloud based player for anyone with a simple web browser and a connection to the Internet to view. This could be Google Docs or Microsoft Cloud/Live, or several free and paid sites that specialize in hosting slideshow presentations - I've used slideshare.com for free in the past. The chief drawback is that you may only use basic slideshow features without additional media (like embedded videos or audio) though they are more sophisticated than they used to be and it wouldn't surprise me if some of those websites now support more complex presentations, perhaps at the subscription level.