Appendix C of "33 Revolutions per Minute: A History of Protest Songs, from Billie Holiday to Green Day" (2011), by Dorian Lynskey. These are in addition to the 33 main songs he covers in the book.
My favorite is "Come In Out of the Rain," by Parliament:
"Happiness and peace!
Is getting more and more out of my reach.
Violence and revolution
Seem to be all that the people wanna preach.
You're gunning down your brothers,
Molesting your sisters and your mothers in the streets.
Whoa-ho, and the president's talking 'bout change,
But nobody's got sense enough to come in out of the rain.
When will the people start getting together,
Learning to live and love one another?
Hey, hey, hey.
When will the people start finding each other,
Learning to give and help one another?
Hey, hey, hey."