hovercraft is described as ' Write your presentations in a text markup language. No slow, limiting GUI, no annoying HTML!'* and is a Slideshow Maker in the development category. There are more than 100 alternatives to hovercraft, not only websites but also apps for a variety of platforms, including Mac, Windows, iPhone and iPad. The best alternative is LibreOffice - Impress, which is both free and Open Source. Other great sites and apps similar to hovercraft are Google Slides, Microsoft Powerpoint, Prezi and Reveal.js.
Prezi allows anyone who can sketch an idea on a napkin to create and perform stunning non-linear presentations with relations, zooming into details, and adjusting to the time left without the need to skip slides.