Generate noise with canvas.

gistfile1.js

// Big up to Jeffrey Way for this noise generator (http://net.tutsplus.com/tutorials/javascript-ajax/how-to-generate-noise-with-canvas/)

function generateNoise(opacity) {
	if (!!!document.createElement('canvas').getContext) {  
		return false;  
	}
	
	var canvas = document.createElement("canvas"),  
	ctx = canvas.getContext('2d'),  
	x, y,  
	number,  
	opacity = opacity || .2;  
	
	canvas.width = 250;
	canvas.height = 250;
	
	for(x = 0; x < canvas.width; x++) {
	  for(y = 0; y < canvas.height; y++) {
	     number = Math.floor(Math.random() * 40);	
	     ctx.fillStyle = "rgba(" + number + "," + number + "," + number + "," + opacity + ")";
	     ctx.fillRect(x, y, 1, 1);
	  }  
	}
	return canvas.toDataURL("image/png");
}

jsfiddle'd: http://jsfiddle.net/LbF5a/

Ahh, good thinkin'