MP3Cutter

MP3Cutter is a simple utility that enables you to cut out pieces of a MP3 without having to decode that MP3 to a non-encoded PCM (wave)-file. MP3Cutter cuts the MP3 at the Frame level so it doesn't degrade the quality of your MP3.

This way of editing has one major downside: special effects like: normalizing, fading and adding things like a flanger or an echo are not possible.

If you want these kind of "effects" you'll need to decode the MP3 stream into an un-encoded PCM format which can then be processed with a program like CoolEdit.