There is a simple App called Fission for taking clips from any section of a MP3 for ringtones on your iPhone, or any other compatible cell phone. It has a very nice custom auto-save to iPhone feature.
You can trim and split audio files with no loss in quality (bitrate or compression) of the sound. Also, you can copy and paste selections of audio anywhere you want in the file, or delete selections altogether.
Supported formats include: MP3, AAC, Apple Lossless, AIFF and WAV.
There's a free demo version available for download, along with a full paid version for $32. It is worth every penny if you want very easy MP3 ringtone clip creation without having to re-encode your files. It is only available for the Mac.
