Are there any good presentation software/websites besides Microsoft Powerpoint that are
- Simple to use
- Doesn't require sign up
I would suggest Prezi.
It is a different way of presenting stuff, but I believe it is much, much better than PP, in that it has large potential for creative and - most importantly - memorable and comprehensive presentations.
Here is the gigantic trouble with traditional powerpoint and similar presentations: It is linear, and linear only. It is mainly suited for images/videos and bullet-lists in sequential models. It is, in a way, a video, in respect to being 1, 2, 3, 4 etc.
As an audience to such presentations, and assuming this is a little more complex than what you could give people in four slides or half a page... people will have to remember a good deal of the points during the presentation.
This is of course possible if it could all fit on half a page. But if it can fit on half a page, you do not need PowerPoint. Give people half a page. Or display the half page only on the screen.
PowerPoint have been misused to the pathetic or even dangerous; with people adding all sorts of nonsensical stuff such as backgrounds, animations, irrelevant images and - the horror - clip art. This often just add to a muddle and not often a tool for learning or decision making.
So. What else?
Presenting well is an art. I am not going to get into how you should present stuff (keep it as simple as possible, but not one bit simpler). I do however believe Prezi is a much better alternative. It is not linear, it is spatial. You can zoom, reiterate, revisit previous points, set it all in context, go back, forward, create overview. Of course it can be misused to the miserable, but I think it certainly is a step forward.
Yes, there is a sign-in. But it is worth it.
(oh, and btw - some browsers have presentation capabillities)
There are some great online tools that you can make presentations on. The big advantage is that they are responsive across multiple platforms, so users can view the slides from the phone, tablet, or computer.
Some I've come across that don't use Flash (like Prezi does) include
Slides.com - My personal favorite of this list because of it's navigation system (vertical in addition to horizontal) and built in transitions.
Swipe.to - Pretty standard, similar to a PowerPoint presentation but responsive
Slideshare.net - Pretty standard, similar to a PowerPoint presentation but responsive
Or you could create your own using a library like FlowTime.js (which is pretty dang sick) or something completely from scratch.
PDFs have a presentation/fullscreen mode. So Indesign or others might be used to create a presentation that can be shown in the same way, but created with another tool. (Of course, there wouldn't be animation. Would that really be a problem though?)