From the Nielsen Company:
PRODUCT CATEGORY AD SPENDING
Spending by the top ten product categories was down 9.5% in 2009. The automotive industry was the top category with over $8 billion spent last year. Pharmaceutical, Quick Service Restaurants, and Department Stores were next on the list, with each category showing year-over-year gains.
While the Automotive category will remain the top Ad spending category, I doubt it will ever return to 2008 spending levels.