Wish you were here - Pink Floyd
http://www.youtube.com/watch?v=q1moiym6-Nk

Feelin' Good Again - Robert Earl Keen (i <3 REK, anyone else?.. no I don't dig on country music in general)
http://www.youtube.com/watch?v=8yURhsraXfc

Unchained (Acoustic) - Johnny Cash and Willie Nelson
http://www.youtube.com/watch?v=5Dqbv8a1Qtg (not the vh1 version)

I'm a total sucker for very simple acoustic stuff...