This may be trivial to experienced users but took me a while to find so...

Online radio including BBC would not play until a search, initiated by a commercial radio station, indicated gstreamer. I don't know exactly which of the applications was missing so I list all those that are now installed:

libgstreamer-plugins-base0.10-0 - GStreamer libraries from the "base" set
libgstreamer0.10-0 - Core GStreamer libraries and elements
gstreamer0.10-alsa - GStreamer plugin for ALSA
gstreamer0.10-plugins-base - GStreamer plugins from the "base" set
gstreamer0.10-plugins-good - GStreamer plugins from the "good" set
gstreamer0.10-tools - Tools for use with GStreamer
gstreamer0.10-gnomevfs - GStreamer plugin for GnomeVFS
totem-gstreamer - A simple media player for the GNOME desktop based on GStreamer
gstreamer0.10-x - GStreamer plugins for X11 and Pango
gstreamer0.10-ffmpeg - FFmpeg plugin for GStreamer
gstreamer0.10-plugins-bad - GStreamer plugins from the "bad" set
gstreamer0.10-plugins-ugly - GStreamer plugins from the "ugly" set

This will also play the "video" output (swirly patterns etc)

However, for youtube, the method was:

In firefox, edit>preferences>applications>shockwaveflashfile
chose /usr/bin/swfdec-player
The dialog box then gave the option "use swfdec flash player". Chose it.

Another reason for posting this is:
There is debate about lack of availability of shockwaveplayer and iplayer within free software (and some sites appear to "need" iplayer). This could be misconstrued (by people like me) to mean that you can't use some of these media except through wine, hence my post 2 days ago.

I have been able to replace several wine tasks with native Linux applications and it feels so much better- and is more reliable.

I will mention Exam cafe now, so that someone searching will be directed here. These educational aids (revision material) will require the link to swfdec-player mentioned above, and that is all; but the documentation issued with the cd suggests that it will only work with w$ or mac. This is really not the case.