A little reminder for me:
for i in *.flv; do ffmpeg -i "$i" -f mp3 -vn -ab 64k -acodec libmp3lame -aq 4 "$i.mp3" ;done
... and furthermore trimming the resulting filenames
for name in *.mp3
do
newname=`echo "$name" | tr " " "_" | sed s/\.flv//`
mv "$name" "$newname"
done