Oh man, Paul De Man... yeah, that's an intense marathon of deconstruction. I actually haven't read Of Grammatology before, but that's one of the central texts. I've gone through (more or less) Writing and Difference and Dissemination, the former of which is another major work of Derrida's. It includes his "Structure, Sign, and Play in the Discourse of the Human Sciences," which put him on the map in America. Dissemination is less read, but it has the famous Pharmakon essay, in which Derrida traces some key internal contradictions of language back etymologically to the original Greek.
Margins of Philosophy I picked up mainly because it includes "The Ends of Man," "White Mythology," and "Signature Event Context," all of which are pretty significant works.