Esto hago, funciona en opera y Mozilla, pero no explorer.
Código:
<script src="rutinas/swfobject.js" type="text/javascript"></script>
<div id="flashcontent">Por si no lo carga</div>
<script type="text/javascript">
var so = new SWFObject("http://www.youtube.com/v/u59ooxvaKuM?rel=0&autoplay=1", "video", "200", "200", "7", "#336699");
so.addParam("quality", "low");
so.addParam("wmode", "transparent");
so.addParam("salign", "t");
so.write("flashcontent");
</script>