wordpress.com-style-youtube-shortcode.php

<?php
// Add this to functions.php in your theme to allow youtube
// video shortcodes like wordpress.com does:
// http://en.support.wordpress.com/videos/youtube/
function youtube_shortcode_func($atts) {
	extract(shortcode_atts(array(
		'youtube' => '',
	), $atts));
	
	$url = $atts[0];
	$url_p = parse_url($url); 
	$url_q = $url_p['query'];
	$q_parts = explode('&amp;', $url_q);
	$youtube = array();
	$legal_parts = array('v', 'w', 'h', 'hd', 'showsearch', 'rel', 'fs');
	foreach($q_parts as $str) {
		list($key, $value) = explode('=', $str);
		if (in_array($key, $legal_parts)) {
			$youtube[$key] = $value;
		}
	}
	 (!isset($youtube['rel'])) {
		$youtube['rel'] = 0;
	}
	 (!isset($youtube['fs'])) {
		$youtube['fs'] = 1;
	}
	return "<object width=\"{$youtube['w']}\" height=\"{$youtube['h']}\"><param name=\"movie\" value=\"http://www.youtube.com/v/{$youtube['v']}&fs={$youtube['fs']}&rel={$youtube['rel']}\"></param><param name=\"allowFullScreen\" value=\"true\"></param><param name=\"allowscriptaccess\" value=\"always\"></param><embed src=\"http://www.youtube.com/v/{$youtube['v']}&fs={$youtube['fs']}&rel={$youtube['rel']}\" type=\"application/x-shockwave-flash\" allowscriptaccess=\"always\" allowfullscreen=\"true\" width=\"{$youtube['w']}\" height=\"{$youtube['h']}\"></embed></object>";

}
add_shortcode('youtube', 'youtube_shortcode_func');
?>