Initially I omitted the firefox support (firefox doesn't play mp3 files) then, when adding it, I needed to convert my mp3 files into oggs. Step forward dir2ogg which is completely perfect:
dir2ogg -d .Will quite happily convert all the mp3 files in the current dir to oggs. What more could you ask for?
Getting it on ubuntu is as simple as:
apt-get install dir2ogg