Create a custom ringtone from an MP3 for an iPhone
Open up Garageband.
Drag an MP3 file into Garageband.
Choose Share –> Send to Ringtone
It’ll tell you to set this bar thing to be under 30 seconds.
Choose Share –> Send to Ringtone again
It’ll then show up in iTunes under ringtones. Tell your iPhone sync area the sync that ringtone and you’re done! It’s easy to do. Honest.
http://docs.info.apple.com/article.html?artnum=307108
