Good MP3 download apps for iPhone?

I have a good MP3 download app for my iPhone, but I have way too much music. I wanted to get another app or two so I can organize my music and keep it less crowded. Can someone recommend a good MP3 download app, that includes artists and playlists (Set up like the music app that comes with the iPhone). I have the one made by BSOsoft, so for those who know, I want one like that. Please help!

I don't min if you have to pay, but free is once too!

Free MP3.It's got a blue icon and I think there's a not free version but i don't know. It's pretty good you can have as much music as you want and you can edit the files as in artist, song name, and lyrics.

Sony Walkman S-544 Series 8 GB Video MP3 Player (Black) unit has great, traditional Sony sound quality. And I write this not even using the headphones yet, but simply from the built-in speakers. Perhaps I'm aging, but I do like to listen to music (and definitely radio) without headphones. This player has a good sound that is very clear and detailed with not much in the low frequency, but real clarity in the mid to high frequencies. Don't expect theater sound with these little guys, but it is respectable - my neighbor even heard it while outside and said it sounds good, and I was surprised he could hear it!