CongBom

To get meta value in front-end, use <code>get_post_meta()</code> with meta key is <code>youtube_id</code>.
Example:
Print YouTube video ID: 
 ID, ‘youtube_id’, true);?>
Thumbnails: 
 <img src="http://img.youtube.com/vi/ID, ‘youtube_id’, true);?>/mqdefault.jpg” alt=”” />
Video player:
<iframe src="http://www.youtube.com/embed/ID, ‘youtube_id’, true); ?>” width=”588″ height=”331″ frameborder=”0″ allowfullscreen>

YouTube metabox

Create YouTube meta-box for post with live preview

Nilambar Sharma

<h3>Source Affix</h3>
This is right plugin for you if you want to add source link to your post. It adds separate meta box for the input of source text. You can use this feature to any Post or Page. Even more, it also supports custom post type. Several plugin settings are also available. You can show sources in comma separated form or in an unordered list. You can append or prepend source to the content.

Source Affix

A plugin for adding source links to your Post. Supports Page and Custom Post Type also.

YouTube metabox vs Source Affix