I just upgraded to the Motorola Droid Bionic. I can't seem to find an option to record my own ringtone and attach it to a contact or transfer a ringtone that I created from a computer on to the phone and assign it to a contact.
Go to the contact you want to assign the ringtone to. The screen should have the contact name at the top, with the contact history, phone number, etc., below. Press the menu button (far left-hand button at bottom). Select 'options'. Use the drop-down box below Ringtone to select the ringtone you want for that contact. Press 'ok' and you're done.