Oh, let’s be real: don’t forget PowerPoint. (Otherwise, you’ll be screwed the next time you absolutely have to have camera-shutter sound effects every time the slides change.)
But for simple, everyday slide shows, you could do a lot worse than S5, which stands for A Simple Standards-Based Slide Show System. It’s been around for months, but I only just stumbled across it.
S5 is a slide show format based entirely on XHTML, CSS, and JavaScript. With one file, you can run a complete slide show and have a printer-friendly version as well. The markup used for the slides is very simple, highly semantic, and completely accessible. Anyone with even a smidgen of familiarity with HTML or XHTML can look at the markup and figure out how to adapt it to their particular needs. Anyone familiar with CSS can create their own slide show theme. It’s totally simple, and it’s totally standards-driven.
Plus it’s free, and released under a Creative Commons license. Yes, there’s some minor geekery required (especially if you want to change the template)… but you’ll practically reek of open-source cachet if you run your next presentation using S5. (Better yet, on Firefox. In Linux. Wearing hemp.)