w32codecs and mplayerplug-in
Ubuntu
You will need the mplayer-mozilla package, as well as the w32codecs package from a 3rd party repository, as shown here.
Suse
This page tells you how to install mplayerplug-in and w32codecs.
Fedora Core
This page has a good howto on installing many media related doodads as well as w32codecs.
Anyone else can grab w32codecs from here, or they can consult their documentation to see whether packages are available.
