<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/OLeZAGLEzcU&hl=ja_JP&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/OLeZAGLEzcU&hl=ja_JP&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

<object><param name="movie" value="http://www.youtube.com/v/●&hl=ja_JP&fs=1&hd=1&fmt=37"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/●&hl=ja_JP&fs=1&hd=1&fmt=37" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true"></embed></object>

.entry object,
.entry embed {
  width: 425px;
  height: 344px;
}

#sidebar object,
#sidebar embed {
  width: 300px;
  height: 246px;
}

<link rel="alternate" type="application/rss+xml" href="http://gdata.youtube.com/feeds/base/users/＊＊＊/favorites?client=ytapi-youtube-user&v=2" title="Youtube - ＊＊＊ さんのお気に入り">

<?php
  $rss = fetch_rss('http://gdata.youtube.com/feeds/base/users/＊＊＊/favorites?client=ytapi-youtube-user&v=2');
  $maxitems = 1;
  $items = array_slice($rss->items, 0, $maxitems);

  if (empty($items)) echo 'No items';
  else
    foreach ( $items as $item ) :
?>
  （表示させる箇所）
<?php endforeach; ?>

http://www.youtube.com/watch?v=HKR8J4uXcTA

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/HKR8J4uXcTA&hl=ja&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/HKR8J4uXcTA&hl=ja&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

<?php
  $rss = fetch_rss('http://gdata.youtube.com/feeds/base/users/＊＊＊/favorites?client=ytapi-youtube-user&v=2');
  $maxitems = 1;
  $items = array_slice($rss->items, 0, $maxitems);

  if (empty($items)) echo 'No items';
  else
    foreach ( $items as $item ) :
?>
  <object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/<?php echo substr($item['link'], 31); ?>&hl=ja&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/<?php echo substr($item['link'], 31); ?>&hl=ja&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>
<?php endforeach; ?>

<?php
  $rss = fetch_rss('http://gdata.youtube.com/feeds/base/users/sutetema/favorites?client=ytapi-youtube-user&v=2');
  $maxitems = 1;
  $items = array_slice($rss->items, 0, $maxitems);

  if (empty($items)) echo 'No items';
  else
    foreach ( $items as $item ) :
?>
  <object width="300" height="243"><param name="movie" value="http://www.youtube.com/v/<?php echo substr($item['link'], 31); ?>&hd=1&hl=ja&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/<?php echo substr($item['link'], 31); ?>&hd=1&hl=ja&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="300" height="243"></embed></object>
<?php endforeach; ?>