I had covered a 23 steps iPhone hack and then an easier 9 step iPhone hack to install custom ringtones onto your new iPhone, if that was not simple enough folks at Efiko have come up with iPhone RingToneMaker which is easily the best option available to add custom ringtones to the iPhone and definitely a lot more user-friendly then the iPhone hacks.
Edit your ringtone:
You can use the audio edit screen to select the section you want to use as your ringtone. With your advanced interface you can even select the ‘Start’ and ‘End’ times precise to the hundredths of a second with the help of a slider.