Is this possible...?

I'm about to buy my first car and I know very little about cars.

All the cars I've seen advertised come with a CD player, but I don't use CDs so that's no good to me. All I use is my mp3 player, so I'm looking for a way to just have speakers and a socket to plug in my mp3 player (like a mini jack socket).

Does anyone know if this is possible? Are there any cars that come with this as standard or would I have to have this system installed by a specialist? If so, any idea how much it would cost?

Any help would be appreciated.

some new cars come with aux in jacks, but on the others you'd need to get an FM mod. Unfortunately those FM mods sound like crap, but without getting a new headunit that has an aux in that's about the only thing you can do.