Best sound quality in compressed audio:
interesting page concerning professional AAC and how it compares to other encoding schemes.
Fraunhofer: Fraunhofer Institute's audio section.
Basic technical documentation.
ID3v2: The official website of the new MP3 tagging
specification. It provides both the formal and informal specification documents of ID3V2.
Mp3.com: Daily updated mp3 news and free music download.
Mpeg.org: Very complete directory of links to mpeg
resources on the net.
VQF.com: Site about the VQF file format.
The Definitive MP3 Benchmark: Good site benchmarking
MP3 players and encoders. There are few technical explanations too.