Just checked it out, doesn't say they are out yet, but it will send you an e-mail when they are - http://register.rockband.com/

If you don't know, the songs included in the 20 are:

1. Honest Bob - Tatooine
2. Against Me! - Stop!
3. Static-X - Push It
4. George Thorogood - Bad to the Bone
5. Blink 182 - Dammit
6. Free - All Right Now
7. Dead Kennedys - Holiday in Cambodia
8. Hot Hot Heat - Bandages
9. Bad Religion - Suffer
10. Turbonegro - All My Friends Are Dead
11. The Haunted - Shadow World
12. Pennywise - The Western World
13. Rancid - Fall Back Down
14. Sublime - Santeria
15. Taking Back Sunday - What's It Feel Like To Be A Ghost
16. The Breeders - Cannonball
17. Sepultura - Refuse/Resist
18. Queens of the Stone Age - No One Knows
19. The Killers - Somebody Told Me
20. Harvey Danger - Cream and Bastards Rise