Express Points is a free Windows and Mac tool for designing and showing slideshow presentations.
The program works much like a (very) simplified PowerPoint. 24 master slide templates help you build your presentation; you can customise each slide with text, bullet points, lists, shapes, images and audio files; and objects can be moved, resized or rotated to suit your needs.
A vertical timeline shows all your slides in sequence. You're able to rearrange and reorganise them as required (or add one of the 34 transitions), and the slideshow can be replayed when required to your audience.
There are plenty of limitations here, of course. Express Points can import PowerPoint PPTX files, for example, but the program will just ignore everything it doesn't support. These can be fairly basic elements, too, like slide backgrounds. The PPTX support may save you time, but don't expect too much.
Your slideshow can't be exported to any kind of stand-alone or third-party format, either. You can't save it as a PPTX file, or video; it's not even possible to export individual slides. The only way to share a presentation is to save it in Express Points' native NPP format, and for the other person to install the program themselves.
Still, Express Points does provide a solid set of basic presentation tools, and even partial PPTX import is better than nothing at all. If you're looking for a lightweight, simple way to create local presentations then we'd give it a try.