In spite of the fact that we constantly hear bout the evils of PowerPoint, and slide show presentations in general, there's a whole raft of online presentation tools you can play with. Some allow you to actually create presentations in your browser, and others simply make it possible for you to store, share, and embed your presentations. Here are some that I have actually used or played with:
Slideshare is the YouTube of the presentation world. It allows you to upload ppt, pps, odp (open office) and pdf files, present them on the site, share them, allow downloads, and embed shows in webpages and blogs. I used slideshare here, and I think it's especially useful if you want to embed a presentation in your web page, AND you want random people to see your stuff. I have already had a few requests to use the shows from other people looking to put on geocaching presentations. No creation capability as yet, but I wouldn't be surprised if that is eventually incorporated. Definitely a social tool.
ZohoShow has creation and editing capabilities that Slideshare does not. However, Zoho isn't nearly as easy to navigate, and the social aspect isn't anywhere near as useful as Slideshare. If you take the time to look around and figure things out, need the editing and creation tools, and are not concerned about the social aspect, then give this a try. Quality of uploaded programs is actually a bit better than Slideshare. They also have other tools, much in the same vein as Google Docs.
Preezo is a cleaner, more straightforward version of ZohoShow. However, no upload function. But you can create, email, share, and embed. No social interface. For straight creation, I like this better than Zoho.
Thumbstacks is one of the earlier players in online slide creation, and operates on a very spare platform. In fact, it's so spare, there's barely any documentation at all. None of the frills of the aforementioned, but it does work. Share slides via a link - no embedding. Minimalists will love it.
Naturally, Google Docs has joined the fray as well. Again, very similar to Preezo; not a lot new going on here. But, I can definitely see the benefit to using this tool if you already use the other Google Docs tools, and I do like the idea of having a complete suite online. If library patrons caught on to this, there'd be less need to outfit each computer with MS Office.
Now, if you know code, have server space, and do a lot of presentations, you might like the system that Jessamyn uses. I have also gone this route, and I love the finished product. If you have zero html/css experience, and don't particularly want any, this probably isn't the way to go. But if you do, once you've done one, doing others is a snap. Also makes it easy to store your presentations on your server and present presentations in link-list format on your web page. Nifty "print" version option as well.
OK, go put something together, and come back and show the class.