You can download mp3Directcut from softpedia and try it. The software is free. If you want to do more than just cutting you can google for audacity.
Hi, mp3DirectCut is impressive but I got some file corruptions after using it, so be wary when you use it. You can check that the file is corrupt when the total time is not right, smaller than it should be.
I'm using Audacity for this purpose also. You will have to download Lame to encode Mp3 files. You can download it from here: http://lame.buanzo.org/#lamewindl