File Stitcher is the easiest MP3 merging utility there is. Simply drag and drop the files you wish to merge on the application icon and click the "Stitch Files" button.
Don`t re-encode your MP3s, File Stitch them together!
(Files must be of the same bit rate, may require pre-processing.)
Trial version available at http://pariahware.com/filestitcher.php
