What exactly is this for? There's a different way I'd do it, using DisplacementMapFilter to get a more realistic effect but I don't think it'd be a good idea to use it at 100% browser window.

I need to do one on the background of a site, that background is 100 percent browser size.
That is swf is set to 100% and noscale.

thanks for the great blog

I don't really know any good places for tutorials, as I've yet to find any "teach yourself Flash" sites worth rating. So many of them still use code embedded on the timeline and other bad practises. That said, I've not really looked recently so there may be some excellent sites out there that I'm missing!

I'd recommend Moock's Essential ActionScript 3 book, it's how I got started toying with BitmapData. Curiosity, the in-built Flash help and blog posts found on Google took me further. I put the source code up for a later version of this flag script, it's not amazingly well written but might help you out a little.

Good luck and let me know how you get on!