Here's a good Joan Baez version, easy-to-learn melody and phrasing for a crowd to sing:http://www.youtube.com/watch?v=4BdTu1IhsSg&feature=related
First verse (only two chords: Cm, G):
Cm G Cm
Ain't gonna let nobody turn me around, turn me around, turn me around
Ain't gonna let nobody turn me around,
Keep on walkin', keep on talkin'
Gonna build a brand new world.
Other verses in Joan Baez version modify first line to reflect issues of the time.
Common earlier versions of song (i.e. from Civil Rights Movement) have last lines similar to: "Marchin' to the Freedom Land" or "Marchin'' to the Freedom Train." Other variations exist, too.
Personally, I like "Marchin' to the Freedom Land" since Occupy is all about Freedom of Speech.