This isn't quite exactly on point since it pre-dates the whole "Occupy" thing, but my friend Tom Kastle wrote a protest song about the protesters being kept out of the capitol building in Madison, Wisconsin earlier this year.   (That was a short-lived situation, they are now allowed back in again.) Here's a video of the song on YouTube: http://youtu.be/lOnxh-7QfM4

Tom reports they've been having daily protest sings in Madison for months. I've pointed out this thread to Tom, he may show up and comment further about that and what they've been singing.