Tonight couldn't sleep so wrote one of the presentations I hope to give at BarCampOrlando this sunday. Used Google presentations, it seems pretty nice so far. The killer feature is that you can run a presentation over the web, and people can follow along, ask questions, etc.
One thing I miss is the ability to put speakers notes in. It would be great to have a separate window popup when you start a presentation that has your speakers notes for each slide, and a couple of timers like the OS X Keynote presentation does: 1 timer for cumulative elapsed time since starting the presentation, and 1 timer for elapsed time on current slide.