The song list shows up at 1:27, and shows the songs categorized by difficulty. Here's the seven "new to us" tracks, which brings the number of known songs up to 52:
The Konks' "29 Fingers"
Flyleaf's "I'm So Sick"
The Mother Hips' "Time We Had"
Anarchy Club's "Blood Doll"
The Acro-Brat's "Day Late, Dollar Short"
Crooked X's "Nightmare"
So, want to let us know the last six, Harmonix? We'll be your best friends in the whole wide world -- promise!
EDIT: Another Joystiq reader tipped us off to a blog posting by the band Honest Bob and the Factory-to-Dealer Incentives stating their song, "I Get By," is in Rock Band. Only five left now!
[Thanks, Brian and Andy]