It's so nice when things work out the way you hoped. There's a handful of new songs available for download in Rock Band Unplugged and the one song we actually want ("Still Alive" by GLaDOS and Jonathan Coulton) is free, totally free. The rest, if you're curious, will run you $1.99 per song:
Dixie Chicks "Sin Wagon"
GLaDOS and Jonathan Coulton "Still Alive" *
The Pixies "Here Comes Your Man"
R.E.M. "Losing My Religion"
Stevie Ray Vaughan "Pride and Joy"
Oh crap, we didn't see "Sin Wagon"! Please, disregard everything we said above.