Free:

• "Halo Theme (MJOLNIR Mix)" by Martin O'Donnell and Michael Salvatori with guitars by Steve Vai
• "We Three Kings" by Steve Ouimette

200 Microsoft Points each:

• "Ernten Was Wir Säen" by Die Fantastischen Vier
• "So Payaso" by Extremoduro
• "Antisocial" by Trust

Free:

Boss Battle Track Pack

• "Tom Morello Guitar Battle" by Tom Morello
• "Slash Guitar Battle" by Slash
• "The Devil Went Down to Georgia" as made famous by The Charlie Daniels Band

500 Microsoft Points each:

Modern Metal Track Pack

• "The Arsonist" by Thrice
• "Hole in the Earth" by Deftones
• "Almost Easy" by Avenged Sevenfold

No Doubt Track Pack

• "Don't Speak" by No Doubt
• "Excuse Me Mr." by No Doubt
• "Sunday Morning" by No Doubt

Classic Rock Track Pack

• "Peace of Mind" by Boston
• "Juke Box Hero" by Foreigner
• "Any Way You Want It" by Journey

Warner/Reprise Track Pack

• "No More Sorrow" by Linkin Park
• "Sleeping Giant" by Mastodon
• "Pretty Handsome Awkward" by The Used

Foo Fighters Pack

• "The Pretender" (from the album Echoes Silence Patience & Grace)
• "All My Life" (from the album One By One)
• "This Is A Call" (from the album Foo Fighters)

Velvet Revolver Pack

• "She Builds Quick Machines" (from the album Libertad)
• "Slither" (from the album Contraband)
• "Messages" (from the album Libertad – Deluxe Edition)

Available by purchasing the Guitar Hero III Soundtrack CD:

Companion Track Pack

• "Carcinogen Crush" by AFI
• "Tina" by Flyleaf
• "Putting Holes in Happiness" by Marilyn Manson