One of the most handy and unique features of AS3 is the ability to select multiple files at once and upload/download them.  There are lots of classes and assorted wackiness out there on the subject, but here’s the upshot (!):

ActionScript 3.0:
[as3]
var list:FileReferenceList = new FileReferenceList();
list.addEventListener(Event.SELECT, selectHandler, false, 0, true);
list.browse();

function selectHandler(event:Event):void{
var request:URLRequest = new URLRequest("upload.php");
var files:Array = FileReferenceList(event.target).fileList;
for (var i:uint = 0, l:uint = files.length; i < l; i++) FileReference(files[i]).upload(request);
};
[/as3]

PHP: