The score itself is phenomenal too; Trent Reznor and Atticus Ross (Nine Inch Nails) did an awesome job. I listened to it before I saw the movie, and I didn't quite see how it would work in a movie, but it fucking worked.
The site for the score is here:
You can buy the score for (it's worth it) from Amazon.com here:
Also, go check out the film. It doesn't matter if you love, hate, or don't give a shit about Facebook. David Fincher is a master filmmaker, and the movie itself is worth the price of admission.