Widget:YouTube
This widget allows you to add a YouTube video player to your wiki page.
Using this widget
To add a video to your page, write down the video ID and paste the following code:
{{#widget:YouTube |id=bgJD9x3zQ-0 |width=640 |height=480 }}
Will give the following result:
Copy to your site
To use this widget on your site, just install the MediaWiki Widgets extension and the copy full source code of this page to your wiki, as an article called Widget:YouTube.