Garageband 4.1.1 Update

Apple released an update for GarageBand, allowing users to create custom ringtones in GarageBand 4.1.1

With GarageBand 4.1.1 you can export your original song, your original audio recordings, or use Apple Loops and iLife jingles to create a custom ringtone for your iPhone.
Here's what you need to do it:
GarageBand 4.1.1 or later
iTunes 7.5 or later
iPhone with software version 1.1.2 or later
To create a custom ringtone
Set up a cycle region that covers the area you wish to use in the GarageBand song. Note: This area must be 40 seconds or less in length.
Once the cycle area has been set, choose Share > Send Ringtone to iTunes.

For additional information, please visit: http://docs.info.apple.com/article.html?artnum=307108