In fact you do not need to install any plugin. You just need to put this code in your post:
<object type="application/x-shockwave-flash" data="http://www.youtube.com/v/XXXX" height="350" width="425"><param name="movie" value="http://www.youtube.com/v/XXXX"><param name="wmode" value="transparent"></object>
All you need to do is change the XXXX for the number of the video you want to show.
For instance if you change XXXX into eZeYVIWz99I ito would became:
<object type="application/x-shockwave-flash" data="http://www.youtube.com/v/eZeYVIWz99I" height="350" width="425"><param name="movie" value="http://www.youtube.com/v/eZeYVIWz99I"><param name="wmode" value="transparent"></object>
See it in action at http://www.conteaqui.com.br