This site is 100% free. You can make a ringtone out of pretty much any audio file you have, the only catch is you have to wait in line like when you download from fileplanet. Or you can pay for credits to have instant downloads. But the wait isn't bad, you can set it to send a text message to your phone once your turn comes.

Mobile17 ^^ :: Create Ringtones and Graphics: online, for free!

Best one i've found, used it for years til I got a phone that I can just transfer mp3s using a usb cord.