John Resig - Computing with JavaScript Web Workers
http://ejohn.org/blog/web-workers/

"A 'worker' is a script that will be loaded and executed in the background. Web Workers provide a way to do this seamlessly, for example: new Worker("worker.js") - available in Firefox, Safari and Chrome - "If you're doing any computation with JavaScript you should definitely opt to use Web Workers if they're available"

Computing with JavaScript Web Workers

"Normally in order to achieve any sort of computation using JavaScript you would need to break your jobs up into tiny chunks and split their execution apart using timers. This is both slow and unimpressive ..."