MPEG-4 Structured Audio  
   Technical information and developer resources from the Machine Listening Group at the MIT Media Laboratory, the official homepage for this format maintained by Eric Scheirer.
   http://sound.media.mit.edu/mpeg4/

MP4-SA Developer Tools  
   John Lazarro and John Wawrzynek from the CS Division, UC Berkeley provide tutorials, downloads, manuals and links related to the Structured Audio format.
   http://www.cs.berkeley.edu/~lazzaro/sa/

Ross Bencina Structured Audio  
   The writer of AudioMulch, free soundsynthesis software, offers a SAOL/SASL reference guide and decoder resources.
   http://www.audiomulch.com/sa/

Structured Audio Open Group  
   The main goal of the SAOG was to implement Structured Audio (SA) in open source applications offering a portal for their users with forum and downloads of samples and software.
   http://lsiwww.epfl.ch/saog/

Audiocoding.com  
   The open source project FAAC includes an AAC encoder and decoder (FAAD2) with source code packages, developer mailing list, knowledge base, news section and user forum.
   http://www.audiocoding.com/

Fraunhofer IIS  
   Information about the different parts of MPEG-4 Natural or General Audio (GA) from one of the inventors of these formats, see also their page about MPEG-2 AAC.
   http://www.iis.fraunhofer.de/amm/techinf/mpeg4/audio.html

MPEG Audio  
   Official site of this MPEG subgroup with FAQs for the different standards, publicly available reference documents and software.
   http://www.tnt.uni-hannover.de/project/mpeg/audio/

ISO/IEC  
   Publicly available standards from the International Organization for Standardization including MPEG-4 with 14496-5 containing the Audio, Visual and Systems parts.
   http://www.iso.org/iso/en/ittf/PubliclyAvailableStandards/

Everwicked.com  
   Comprehensive guides about DivX, XviD and MPEG4IP, a forum and other resources about digital audio/video coding and streaming.
   http://www.everwicked.com/

Doom9  
   Besides this forum for audio codecs there are others for container formats and video encoding in general with FAQs.
   http://forum.doom9.org/forumdisplay.php?forumid=11

Mp4-tech  
   The web archive of the public MPEG Industry Forum mailing list with many knowledgeable participants from companies like FhG, Apple and Microsoft.
   http://lists.mpegif.org/pipermail/mp4-tech/

Coding Technologies  
   Company that invented Spectral Band Replication (SBR) and combined it with MP3 (mp3PRO) and AAC (aacPlus or HE AAC).
   http://www.codingtechnologies.com/

Via Licensing  
   Patent pool administrator for AAC with FAQs and overviews of royalty fees for commercial implementations.
   http://www.vialicensing.com/

QuickTime development  
   Apple offers technical FAQs, knowledge base and publicly available documentation files including the MOV file format.
   http://developer.apple.com/quicktime/

Mayah  
   Hard- and software company for professional broadcasting products with AAC/MP4 support.
   http://www.mayah.com/

AES Publications  
   All available articles and documents from the Journal of Audio Engineering Society with search tool including a CD about coding artifacts.
   http://www.aes.org/publications/

Nokia developer forum  
   Platform to support the implementation of their software SDKs including AAC/MP4.
   http://discussion.forum.nokia.com/forum/

Faac.sourceforge.net  
   The old Audiocoding.com forum is still available providing valuable content like FAAC compiling issues with its search tool.
   http://faac.sourceforge.net/oldsite/phorum/

Machine Listening  
   Reading list for an MIT seminar, most of the mentioned publications are directly available on their web server or linked to Amazon's book section.
   http://web.media.mit.edu/~tristan/Classes/MAS.945/technical.html

Telos Systems  
   Hardware manufacturer of the Zephyr ISDN codecs for radio and television broadcasters providing articles and brochures about different AAC implementations.
   http://www.telos-systems.com/techtalk/

Dissertation of Dr. Ye Wang  
   "Selected advances in audio compression and compressed domain processing", comprehensive overview of internet and mobile communication codecs and new methods for improvement. [PDF]
   http://sivut.koti.soon.fi/lasse55/wangye_PhD_final%20collated.pdf

Roberto's listening tests  
   Provides public group comparisons of several AAC codecs and other formats at different bitrates.
   http://www.rjamorim.com/test/

Tuner2  
   List of internet radio stations using aacPlus for their low bitrate streams, among them SomaFM.com and Boomer Radio.
   http://www.tuner2.com/

MPEG4.net  
   Resource for news, information and products about MPEG-4, H.264, Windows Media, High-Definition, Streaming Media and related technologies.
   http://www.mpeg4.net/

MPEG LA  
   Patent pool administrator for the MPEG-4 Systems part of the standard including the MP4 file format.
   http://www.mpegla.com/m4s/

3GPP SA4  
   This working group of the standardization organization deals with codecs like enhanced aacPlus or AMR-WB+ used in mobile telecommunication.
   http://www.3gpp.org/TB/SA/SA4/SA4.htm

Apple  
   Overview of their implementation and contribution to the MPEG-4 standard.
   http://www.apple.com/mpeg4/

Digital Radio Mondiale  
   DRM is a world-wide initiative to use analog AM radio for digital sound and services implementing aacPlus at very low bitrates, often mixed up with Digital Rights Management for copy protection.
   http://www.drm.org/

EE Times  
   "Meeting MPEG-4 advanced audio coding requirements", knowledgeable article summarizing the most important properties of AAC for hardware playback.
   http://www.eetimes.com/article/printableArticle.jhtml?articleID=12801919&url_prefix=story&sub_taxonomyID=

Audio Research Labs  
   ARL is a commercial laboratory involved in subjective quality assessment methods like preparing and analyzing codec comparisons for 3GPP.
   http://www.audioresearchlabs.com/

Facial Animation  
   AT&T Labs develops a computer human interface using 2D and 3D talking head-and-shoulder models driven by a Text-To-Speech synthesizer (TTS).
   http://www.research.att.com/projects/AnimatedHead/

Text-To-Speech Synthesis  
   Bell Labs' / Lucent Technologies multi-lingual TTS demos and introduction to this coding method.
   http://www.bell-labs.com/project/tts/

Speech Synthesis Examples  
   Many TTS demos in several languages from different systems with links to their homepages.
   http://www.ims.uni-stuttgart.de/~moehler/synthspeech/

IBM Composite Media Group  
   Overview of their implementation and contribution to the MPEG-4 standard, especially for the Systems part.
   http://www.research.ibm.com/mpeg4/Projects/

Mobiledia  
   Reviews, articles and forum discussions about cell phones capable of AAC/MP4/3GP playback (also called "iTunes" format sometimes, use the site search).
   http://www.mobiledia.com/