According to TwilightTheSoundtrack.com:
We are happy to announce that the New Moon soundtrack will be in stores on October 13th! That will give you all plenty of time to get to know the music before the movie is in theaters on November 20th. As Chris Weitz has mentioned, artists such as Thom Yorke, Bon Iver, Muse, and Band of Skulls are being discussed for the soundtrack but nothing is confirmed so far. Stay tuned to www.newmoonthesoundtrack.com for exciting information about the official soundtrack pre-order, which will get you tons of extras and exclusives before the album arrives!