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: 
Javascript virtual machines in the future will have a method JIT and a tracing JIT like firefox 4 and JägerMonkey/TraceMonkey.
General details can be found at wikipedia.org and more detail at the Sun microsystems website and its links to associated sites. Some techniques now in use with recent versions of IE and Firefox and other browsers are forms of dualprocess or multiprocess operating in their own control structure to enhance performance specifically and for improving the general browsing experience. The use of javascript is decreasing in some nations and increasing in others as the relevant public internet server population changes over time. Only when the javascript parsing and interpreting code is rewritten in a faster language or some form of multiprocess is introduced to code on the servers or operating in the user's computer will the speed increase.