In case you have an ogg vorbis file and need to transform that to a MP3 file (for example for mobile phones or crappy mobile audio players) the following command line will transform all ogg files of the directory to mp3 files. Please keep in mind that you will lose audio quality when you transform one lossy audio format to another.
for file in *.ogg;do oggdec -o - "$file"|lame -h -V 4 –-vbr-new - "$(basename "$file" .ogg).mp3";done
I am aware that there are thousand other methods – you could write entire scripts, GUIs, use other tools, and so on. But this way works for me, and I need some place to remember it. In case you wonder: if you want to increase the qualit, change the “4” to a “2”. This of course only makes sense if you have a high quality ogg vorbis file. :)