Spotify music streaming seems to be actually quite good, or so I've heard.
Anyhow moving on, I don't think it's worth the hassle of going through several music downloads sites just to find one lousy little mp3 track. If you're into music streaming internet radios thing, these are well worth it.
Just find'em, play'em and you can happily sing along in a matter of minutes. Besides shoutcast, think penguinradio also has quite a large database of internet streaming radio stations arranged accordingly to genre or something like this.
Plus if can't ditch the need to download mp3 tracks or just need some fresh music for any mobile devices you can just record music from streaming radios and convert web radio music to mp3 tracks. There's some audials piece of software that can record mp3 music from internet radios, for example:
http://audials.com/en...row-a-mega-party.html
Think it's quite a good solution to the mp3 music downloads new sources search; at least for me.