Read it once and keep up with new posts.
The truth is there's just no one good answer to this. There are far too many artists and record labels in the world for there to be a concise list of every single new release, that doesn't involve some sifting through to find the stuff that interests one particular person.
Also, regarding the comment about having a thread for each band/artist, that's already the case. And in most cases when someone finds out about a new release from an artist, they'll post a comment to the thread.