> Is there a way to play youtube videos with Mplayer. Externally without using OWB?

There is a recent ARexx script for this purpose:

http://os4depot.net/index.php?function=showfile&file=video/misc/yt.lha

An older version has been adapted to MorphOS:

http://www.pegasosforum.de/viewtopic.php?p=53439#p53439