I came across this article and accompanying video today, giving an excellent and clear explanation of digital audio, sample rates, and bit rates. It clears up many of the myths and misconceptions about digital audio, including the notion that higher sample rates result in a noticeable improvement in audio quality. The video is excellent – definitely watch it. The article is also excellent, and more in depth.
Article on xiph.org: 24/192 Music Downloads are very silly indeed
23 minute video: Digital Show and Tell