Ring tones are a multi-billion dollar business that Leo doesn't think should exist at all if the user already owns a song. iTunes used to convert songs to ring tones, but they took it out so they could sell ring tones. He can still create a ring tone using iTunes though. He could also create a ring tone in an Android phone through the settings on the music player, or through DoubleTwist.
The problem with free ring tones that are available to download is that a lot of times they're spyware or worse. Definitely don't put a free ringtone program on the phone. The safest way to do this with a feature phone is to just pay for the ring tones through the wireless carrier.