I have been doing this for about 3 months now. Not only can you get the full songs, but you occasionally find some really good remixes. Go to the URL posted below and search for the song/artist.

http://www.flashflashrevolution.com/sims/

many of you have probably visited this site. For those of you that haven't, it's a form of DDR for your fingers. Anyway, it's really easy to get the song file out. You just go into the folder and it's right there, in MP3 format.