You can record radio stations over the internet and get a lot of mp3's this way.
You can use a software like
www.stationripper.com which is free and easy to use.
Or if you want something more professional and a lot of features, then you can pay a few bucks and get a software like iRadio, Replay Radio, Skado, but my favourite is
www.radiotracker.com
Your decision :P