reveal.js is an open source HTML presentation framework. It enables anyone with a web browser to create beautiful presentations for free. Check out the live demo at revealjs.com.
The framework comes with a powerful feature set including nested slides, Markdown support, Auto-Animate, PDF export, speaker notes, LaTeX typesetting, syntax highlighted code and an extensive API.
Want to create reveal.js presentation in a graphical editor? Try https://slides.com. It's made by the same people behind reveal.js.