Here`s a free php youtube video downloader script.

It can be integrated in wordpress or any other site that uses php.
You can use it as by linking to yoursite/youtube.php or by including it with a iframe.

To include it with a iframe you have to upload youtube.php to your blog and then go to the wp-admin and create a new post or page. Put the following code there:

<iframe src="http://your site/path to youtube.php">

I hope you enjoy it!
Download:
youtube video downloader
Demo: