Actually, i think it was BrenR who years back posted a variety of mp3s on the forums that demonstrated various things such as clipping, differences b/w sampling rates, bit rates, distortion levels, etc.
If someone can link to that post, i'll add it to my favorites. Assuming the links to his mp3 samples are still active.
(my apologies if it was someone else that posted the samples, ClubNeon maybe?)

"Those who preach the myths of audio are ignorant of truth."