Real Uploader is extremely simple to install in your web site. Just include the single Javascript file and the style and you're ready to go.
<head>
<link rel="stylesheet" type="text/css" href="css/minimal.css" />
<script src="js/RealUploader.js"></script>
</head>
<div class="targetElement"></div>
var uploader = new RealUploader(".targetElement", {
url:'upload.php'
});