package 
{
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.MouseEvent;
	import flash.net.navigateToURL;
	import flash.net.URLLoader;
	import flash.net.URLRequest;
	import flash.net.URLLoaderDataFormat;
	
	public class Main extends Sprite 
	{
		private var tinyLoader:URLLoader
		
		public function Main():void 
		{
			if (stage) init();
			else addEventListener(Event.ADDED_TO_STAGE, init);
		}
		
		private function init(e:Event = null):void 
		{
			removeEventListener(Event.ADDED_TO_STAGE, init);
			stage.addEventListener(MouseEvent.CLICK, postToTwitter);
			tinyLoader  = new URLLoader();
			tinyLoader.dataFormat = URLLoaderDataFormat.TEXT;
			tinyLoader.addEventListener(Event.COMPLETE, gotTinyURL);
		}
		
		private function postToTwitter(event:MouseEvent):void {
			trace("postToTwitter()");
			tinyLoader.load(new URLRequest('http://tinyurl.com/api-create.php?url=http://www.adrianparr.com'));
		}
		
		private function gotTinyURL(event:Event):void {
			trace(tinyLoader.data);
			var reqString:String =  'http://twitter.com/home?status=Check this out ' +  encodeURIComponent(tinyLoader.data);
			navigateToURL(new URLRequest(reqString), "_blank");
		}
		
	}
	
}

http://www.nayansavla.com/blog/?p=253

AS3 Post tinyurl to Twitter via Twitter webpage

post, twitter

ActionScript 3