If you have tried watching a youtube video on a psubuntu installation you have probably been greeted with the message:

Hello, you either have JavaScript turned off or an old version of Adobe’s Flash Player.

The reason for this is that Ubuntu only includes completely free software, which excludes media formats controlled by patents or license restrictions.

While there is currently no Flash version for the PowerPC architecture, you can try installing the free SWF movie player Gnash and its firefox plugin to watch youtube videos:

sudo apt-get install gnash mozilla-plugin-gnash

Restricted extras

Another way to get Gnash is to install the restricted extras package. ubuntu-restricted-extras gives you a lot of useful functionality, like Java, common fonts and multimedia formats. Install with the command:

sudo apt-get install ubuntu-restricted-extras

Note that there is also xubuntu-restricted-extras (for Xubuntu) and kubuntu-restricted-extras (for Kubuntu).

See this forum thread for more information.

UPDATE:

SwiftBiscuit has posted a tutorial on how to use mplayer instead of gnash for improved youtube video playback. Using the Firefox extension Greasemonkey and this user script, you will be able to improve the quality of video playback on web pages.

Forum thread in PSUbunTutorials