Here is a pretty interesting read on the mechanics of dithering audio files.
For the most part it applies to their software, but it is very informative.
PDF file:
http://izotope.com/products/audio/ozone/OzoneDitheringGuide.pdf (http://izotope.com/products/audio/ozone/OzoneDitheringGuide.pdf)
Associated sound files:
http://izotope.com/products/audio/ozone/dither_files.zip (http://izotope.com/products/audio/ozone/dither_files.zip)