I have an IPod shuffle (the little one).
It's tiny and weighs nothing, holds around 250 songs or about 15-20 hours of music.
Just set up your play list, download, press play and ride on. all of the controls, (play, pause, up, down, volume) is on the single button.
You can't choose your songs on a screen or anything, but when your riding, why would you want to?
The battery lasts forever, but be nuclear or something. I played mine for about 2 weeks straight and never got below 30% on the charge.
It only costs around 70 bucks, probably less now, or you can find one on ebay or craigslist, (watch out for Criss Hanson
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).
Get the ear buds that shove in your ears. Your biggest issue is going to be drowning out the outside noise so you can hear your tunes. They set up the MP3 players so you can only get so many decibles out now, not near enough for me, but a life time of loud clubs and playing with automatic weapons and explosives has made my hearing less than stealler.
No need to spend the big bucks on ear buds, you are not going to hear the "crystal clear" sounds of Enya anyway.