There are many articles and web pages about audio compression on the Internet. Unfortunately many of them are out dated, inaccurate or just plain crap written by people who know nothing about the issue.
'Garf', a member of OGG Vorbis development team, has made a review page that analysis audio encoder comparisons made by others. This is very educative reading for anyone interested in digital audio compression.
Objectively comparing perceptual audio codecs
Objectively comparing perceptual audio codecs
