mp3DirectCut: is a small tool for editing MPEG audio directly. You can remove parts, change the volume, split files or copy regions to new files.
MP3Cutter: is a program that enables you to cut pieces from a MP3 without compromising the original quality of this MP3.
CUE Splitter: is a freeware tool that split a single big audio track, mostly an album or a compilation, into the relative individual audio tracks, using informations contained in the associated "CUE" file.
MP3Clip: can split and join back mp3 files based on time segments.