There's a great website called Occupy Design that makes available for download protest signs, logistical signs, infographics, and icons.
In their own words: "OccupyDesign is an independent, unaffiliated, and nonpartisan grassroots initiative." It is "a grassroots project connecting designers with on-the-ground demonstrators in the Occupy Together movement. The project’s goal is to create freely available visual tools around a common graphic language to unite the 99%. The project places an emphasis on producing infographics and icons to improve the communication of the movement’s messages and the data surrounding them across the world."
Designers can jump on board and contribute their own ideas, and Occupiers are free to "Find --> Print --> Demonstrate" these visuals.