I was on a project a while back where this cropped up, I never found the solution. I'll know for next time, thanks!

If I'm not mistaken, this happens with IE7 also. I've been playing around with mootools animation and I came across the very same problem. I didn't realize it was a syptom of the body size changing, but after reading this it makes perfect sense. I have been fighting with this problem for about a week (only about an hours time, because it's my own site and I can only handle so much frustration on my own behalf).

Your timing is pretty good for me on this. Thanks.

yesterday I read about object.watch ( http://devguru.com/technologies/javascript/10770.asp )

may be you could watch document.documentElement.clientHeight ( or clientWidth). I haven't see any where to use watch, but I don't know the reason.

You should read this:
http://ecmascript.stchur.com/2006/08/20/beating-the-ie-resize-bug/#more-23

I was driven insane by this problem when working with a resolution dependent layout. IE was flickering and running really slow everytime I toggled a container that would span over the fold as it fired IE into action due to the body resize.

@Charlie - Nice find.

I've also found that JavaScript expressions wrapped in a conditional comment can also work. (With the caveat that they're not that extra pretty and they have a little "bounce" after the resize occurs.)

A quick Google search turned up this example, which kind of illustrates the point:
http://blog.richnetapps.com/index.php?p=49&more=1&c=1&tb=1&pb=1

It's much more roundabout than simply pinging an element's width attribute, though. (But it still remains a nice standby for emulating min-width/max-width in IE6 and below).

What happens if you want Firefox to emulate IE? Not often this happens granted, but I was looking to resize an image to 100/100% of the body - using JS to keep the image ratio, so it doesnt start to look odd.

If you do this in Firefox you get a resize event after you have resized rather than during as in IE. resize v resized...Otherwise I'm just going to scale the image to the greatest extent that the browser can be in order to overcome the problem...

Thought I'd mention, I was having a similar problem and made my own test page. On my test page though I wasn't seeing the resize event being called for document body changes. Then I compared my test page and my problem page and it turns out this doesn't happen if you have a strict DTD. If you have a transitional DTD though it doesn't occur. The strict DTD page also had the XML declaration so it might be related to that.

@steve - Maybe it fires three events because of width, height, and zoom...

I had similar problem. I was adjusting the buttons width during onload, but that triggers on resize event in IE. My fix was:

/**
* onload handler
*/
handleOnLoad = function(evt)
{
	var docResizeHandler = null;
	if (myVars.browser.name == "MSIE")
	{
		docResizeHandler = (document.body.onresize) ? document.body.onresize : null;
		document.body.onresize = null;
	}

	// Fix buttons width code
	... ... ...

	if (myVars.browser.name == "MSIE")
	{
		document.body.onresize = docResizeHandler;
	}
}

/**
* onresize handler
*/
handleResize = function(evt)
{
	var ieEvt = window.event;

	if (myVars.browser.name != "MSIE" || ieEvt.type == "resize")
	{
		// Handle resizing
		... ... ...
	}
};