Presentation is a standards-based HTML/ECMAScript/CSS presentation system. It supports some limited backwards compatability with S5, xoxo, and Opera Show Format--but if anyone's concerned with improving this I'll accept patches.
See the presentation demo to get a better feeling.
You can download or link to the necessary files which are currently at v0.4
The current development version is currently at v0.5, which is unstable, and to which I do not suggest hot-linking.