I’m not terribly knowledgeable about folk music, but I think the best folk music speaks truth to power and I don’t know many folk musicians who have done it better than Utah Phillips. I stumbled across him in a response to a post on the Common Dreams site and started searching for more information about him. Here is a portion of an interview with him, done by Amy Goodman, of Democracy Now!

Here is a sample of his style of protest:
Talking NPR Blues

There is more available about Utah Phillips both on YouTube and on his web site. Perhaps folk music aficionados out there could point me to more singers who draw from the artesian well of social outrages.