HopSlide is a HOP tool for authoring and playing slides. It supports animations, annotations (slide overlays), math formulas (MathML support and TeX syntax support), SVG images, and canvas graphical effects. HopSlide can be used to compile slides into XHTML files. These files can be used by XHTML capable browsers (e.g., Firefox). Compiled slides files can be used to play the slides without HopSlide.
Zoho Show is an online tool to create, edit, publish, and show presentations. It's web-based. So, you don't need to download or install anything. All you need is a browser (Firefox 1.0 + or IE 6.0+ or Mozilla) and internet connection.