I signed up at 3gupload.com, they give you an online locker where you can put mp3's (if your phone supports it). Once you get it on there you point your phone's web browser to the website, log on and download your ringtone. I have the go go sox fight song, and hawk's homerun call as a couple of my ringtones.
EDIT: They don't give you a online locker, you have to sign up for it, but its not bad, its something like 6 months for 13 bucks.