Question: I know a fair amount about the current javascript engines. What techniques have arisen in the intervening time? Please provide links to freely available information.

edit:

To clarify, I'm looking for new techniques that are being implemented or have recently been thought up for improving javascript execution speed.

Answer: 
Here are some references that came from the top of my head:

* [V8](http://code.google.com/apis/v8/intro.html)
* [Webkit](http://trac.webkit.org/wiki)
* [Spidermonkey](http://www.mozilla.org/js/spidermonkey/)
* [Gecko](https://wiki.mozilla.org/Gecko%3aHome_Page)
* [accelerated compositing in Chrome](http://www.chromium.org/developers/design-documents/gpu-accelerated-compositing-in-chrome)
* [Native Client](http://code.google.com/p/nativeclient/)
* [WebGL](http://en.wikipedia.org/wiki/WebGL)
* [installable web apps](http://code.google.com/chrome/apps/)
* [crankshaft](http://blog.chromium.org/2010/12/new-crankshaft-for-v8.html)

Please notice that at this moment (in the modern browsers) javascript isn't the bottleneck anymore in execution speed of the page. now that that problem is solved a lot of the browser manufacturers are focusing more on other aspects in the process of bringing a page from the server to the user. For instance a lot of the graphically rich pages that are standard now would benefit from the power of modern GPU's. It is often overlooked but rendering a typical page now takes generally more time than executing its scripts.
They [use the GPU](http://blogs.nvidia.com/ntersect/2010/09/next-killer-app-for-gpus-internet-explorer-9-beta-launch.html).