The Energy Department's weekly survey of filling stations showed little change at the pumps over the past week. Nationally, prices were up a penny to an average of $2.639 a gallon. In a possible sign of an improving financial situation, or at least a more optimistic outlook among motorists, AAA last week predicted a 1.4 percent increase in the number of people expected to take to the roads during the holiday. About 38.4 million people will drive at least 50 miles over the course of the holiday, AAA said. That's despite gasoline prices last year averaging nearly 74.7 cents a gallon less nationally. 