If you're going portable, ditch the CD players, and the MP3 players. I've had my Minidisc portable for about 9months now, and couldn't picture myself without it. It's small, media's cheap, plenty of space ( 3hrs on LP2, 5 on LP4 ). What more could you ask for? It is almost impossible to skip, I can play about 30+ hours on ONE AA battery, and I have a older model. The newer ones get more efficient with every new generation. If you buy a new NetMD model, you get to drag and drop songs onto the Minidisc, very sweet.
Check it out:
http://www.minidisc.org