Where can I download mp3s legitimatly for songs in the charts?

Please don't nod your heads back and laugh at me.....I'm being serious I'm too scared to download any mp3s ilegally I've heard too many horror storys of little girls being sued for afew grand for downloading nursery rhymes....

Mods if your thinking about moving my post to a more appropriate forums I won't mind at all just thought it would fit good here since, legitimate mp3 downloading usally involes paying money there for making you a consumer.

Thank you fellow cdrom-guidians