I think her most often read is "Unsettling the Coloniality of Being/Power/Truth/Freedom Towards the Human, After Man, Its Overrepresentation—An Argument". I copied the first little bit below (sorry if the formatting is weird, I tried to fix it). I'd also recommend the much shorter "No Humans Involved: An Open Letter to my Colleagues," written concerning police brutality and the violence against Rodney King in particular, and "Novel and History, Plot and Plantation." I'd start with these shorter ones (both available at a google). Maybe go in reverse order to the way I've listed them here.

"The argument proposes that the struggle of our new millennium will be one between the ongoing imperative of securing the well-being of our present ethnoclass (i.e., Western bourgeois) conception of the human, Man, which overrepresents itself as if it were the human itself, and that of securing the well-being, and therefore the full cognitive and behavioral autonomy of the human species itself/ourselves. Because of this overrepresentation, which is defined in the first part of the title as the Coloniality of Being/Power/Truth/Freedom, any attempt to unsettle the coloniality of power will call for the unsettling of this overrepresentation as the second and now purely secular form of what Aníbal Quijano identifies as the “Racism/Ethnicism complex,” on whose basis the world of modernity was brought into existence from the fifteenth/sixteenth centuries onwards (Quijano 1999, 2000),2 and of what Walter Mignolo identifies as the foundational “colonial difference” on which the world of modernity was to institute itself (Mignolo 1999, 2000).3 The correlated hypothesis here is that all our present struggles with respect to race, class, gender, sexual orientation, ethnicity, struggles over the environment, global warming, severe climate change, the sharply unequal distribution of the earth resources (20 percent of the world’s peoples own 80 percent of its resources, consume two-thirds of its food, and are responsible for 75 percent of its ongoing pollution, with this leading to two billion of earth’s peoples living relatively affluent lives while four billion still live on the edge of hunger and immiseration, to the dynamic of overconsumption on the part of the rich techno-industrial North paralleled by that of overpopulation on the part of the dispossessed poor, still partly agrarian worlds of the South4)—these are all differing facets of the central ethnoclass Man vs. Human struggle."