I use free lossless mp3DirectCut to split mp3 files:

mp3DirectCut is a frame editor for MPEG audio. It makes cutting of even large tracks quick and easy with its fast graphic view. You can make selections to cut, save several regions or modify the volume.

There is no quality loss at all because nothing of your file will be re-encoded. You can prelisten the whole file and even record new MP3s directly to disk.

www.mpesch3.de