Pre- and Post-Katrina  Patricia Gay, Executive Director, Preservation Resource Center of New Orleans, describes how her city's historic architecture has fared in the wake of Hurricane Katrina in a free illustrated lecture, New Orleans Preservation: Before and After a Disaster, 4:30 p.m. at the Old Centrum, 12th and Central. Patty shows the results of her organization's work in the lower Ninth Ward and other flood-damaged districts, and how much remains to be done nearly three years after Katrina.  Stay for snacks—New Orleans cuisine catered by Yats (stay spelled backwards).