Mozilla Shumway an HTML5 JS renderer for SWF files for Firefox

Shumway is an HTML5 technology experiment that explores building a faithful and efficient renderer for the SWF file format without native code assistance. Many have found it to be an effective path away from Flash into HTML5.

It's community-driven and supported by Mozilla. The goal is to create a general-purpose, web standards-based platform for parsing and rendering SWFs. Integration with Firefox is a possibility if the experiment proves successful.

All of Shumway’s rendering occurs using the HTML5 canvas element, as you might expect. And it turns out, once again, that JavaScript is actually fast enough to make this work well. 

Here is a great little racing demo, that is particularly interesting, as it shows that the performance of the ActionScript and graphics engines are fast enough to run real world Flash applications. JavaScript performance is getting really good these days, and many people still underestimate it.