I just got an email about Tuneroom,(redirects to http://www.sideload.com/m) the latest idea from MP3tunes and it’s pretty slick. You just search for a track, choose your file quality and download away. All for free!
I gave it a quick try and it’s definitely worth a bookmark for when you want to grab something on the go. You can either download from your browser of have the file sent via SMS.