Let's make a list of useful website as well.
So here is the list, one post per website in order to edit it with comments if needed.
Musicdsp.org is a collection of data, gathered for the music dsp community.
URL: http://www.musicdsp.org (http://www.musicdsp.org)
The Audiocoding.com Wiki. This Wiki is used to collect all available informations about audio coding and create a "user knowledge base" this way.
URL: http://www.audiocoding.com/wiki (http://www.audiocoding.com/wiki)