I have been trying to find this one as well, as far as I can remember it is something like....

First they came for they jews,
I am not a jew so I did not speak up
Then they came for the communists,
I am not communinist so I said nothing
Then they came for the disabled,
I am not disabled so I said nothing
Then they came for me,
There was nobody left to speak up for me

I have missed a few lines out, does anybody know the rest or who wrote it?