hej,
if you want to have a more or less hardware solution you could go for a industrie mp3 player, which you can controll true the tx at the arduino (printbyte, etc). there is a guy in stockholm salling this stuff (jesper hansen, yampp), but i guess you could find this things also some where else, ...
if you want to i could send you a tutorial by Marcus Hannerstig (from k3).
regards
tomek