This page is basically a few words about some applications which are (IMHO) essential if you are interested in MP3 under Linux.
I can't be bothered with putting links here. If you aren't smart enough to find these apps, you're probably not smart enough to use them.

X11Amp is the only (no, not literally) way to play MP3 files under Linux.
It has a spectrum analyser (and probably a graphic equalizer by now).
It also looks very cool.

If you want to 'rip' audio tracks from cd's and save them as WAV files (or similar), then you need cdparanoia. There are others, but this is the best. You just tell it how paranoid/patient you are, and it does the rest.

So, you've just created a cd's worth of WAV files on your hard disk. Want to see that 650Mb of files become just 65Mb? You need an MP3 encoder. You get what you pay for with these.

• 8hz-mp3
  This is a free (or is it shareware?) encoder.
  It is very basic, and gave me poor results on a number of tracks.
  If you don't want to part with any money, this is probably your only option.

• mp3enc30, mp3enc31
  These are commercial encoders.
  Except there are demos with 30 day licence agreements. Oh, and they will only convert the first 30 seconds of your track.
  The sound quality, however, is superb.
  If you want the best, you will probably want to buy the full commercial version of this program.
  

  Actually, mp3enc30 suffers from some bugs which seriously affect sound quality - though you wouldn't know it with some speakers. This is fixed in mp3enc31.

  You may also find it helpful to know that the 30 second restriction on the demo version can easily be removed. I am not sure of the legalities here, so in no way do I suggest you do this.
  These gdb scripts show how: mp3enc.txt, mp3enc31.txt.