Rock Band Unplugged gets 5 new songs added alongside the 14 DLC songs already available via PSN.

Dixie Chicks - Sin Wagon
Jonathan Coulton - Still Alive (The Portal Song)
The Pixies - Here Comes Your Man
REM - Losing My Religion
Stevie Ray Vaughan - Pride and Joy

As usual, the songs are all masters and are $1.99 per track