SOURCE

//检测插件(在IE中无效)
	function hasPlugin(name){
		name = name.toLowerCase();
		for(var i=0; i < navigator.plugins.length; i++){
			if(navigator.plugins[i].name.toLowerCase().indexOf(name) > -1){
				return true;
			}
		}
		return false;
	}
	
	//检测Flash
	alert(hasPlugin("Flash"));
	
	//检测QuickTime
	alert(hasPlugin("QuickTime"));