You can use setTimeout() and clearTimeout()

function resizedw(){
    // Haven't resized in 100ms!
}

var doit;
window.onresize = function(){
  clearTimeout(doit);
  doit = setTimeout(resizedw, 100);
};

Code example on jsfiddle.

I had luck with the following recommendation: http://forum.jquery.com/topic/the-resizeend-event

Here's the code so you don't have to dig through his post's link & source:

var rtime;
var timeout = false;
var delta = 200;
$(window).resize(function() {
    rtime = new Date();
    if (timeout === false) {
        timeout = true;
        setTimeout(resizeend, delta);
    }
});

function resizeend() {
    if (new Date() - rtime < delta) {
        setTimeout(resizeend, delta);
    } else {
        timeout = false;
        alert('Done resizing');
    }               
}

Thanks sime.vidas for the code!

This is the code that I write according to @Mark Coleman answer:

$(window).resize(function() {
    clearTimeout(window.resizedFinished);
    window.resizedFinished = setTimeout(function(){
        console.log('Resized finished.');
    }, 250);
});

Thanks Mark!