Legal or illegal?... for legal songs.. I would try www.acidplanet.com -> songs created by artists themselves (most with no labels)
Not free, but cheap. www.napster.com Then,,,, http://www.tunebite.com Total cost of about $40, a MASSIVE audio library that you can now (with Tunebite) put on your IPod!
Easiest way: Install Winamp Install Streamripper plugin Search for some good internet radio stations When you hear a good song, click the plugin to start ripping it. Most stations play at over 96kbps which is fine for my ears. Stream ripping breaks apart songs by their names and does some other neat stuff. Google the names if you dont know where to find them.
http://purevolume.com ftw or I heard fbi.gov have some cool tunes if you're looking to pirate music >_>