For a bit of a change of pace, how about "Cocaine Blues" a la Reverend Gary Davis? Or maybe "Corrina Corrina" (not the dead version). Or any of those folk songs.
What about some pigpen? (I'd embed the video but it's an hour long) http://www.youtube.com/watch?v=5sa0qqVVSQ0
These songs would be good for acoustic arrangements: get a bass player and two guitars and you can really jam out with them.
A personal favorite is a twelve bar blues constructed of a Spanish Phrygian (or Phrygian Dominant) scale: 1 b2 3 4 5 b6 b7. Very gypsy. This is really cool for acoustic music.