Google has introduced AdPlanner, which offers traffic and audience profile information for agencies and marketers. Danny Sullivan has a good post showing how it works. It intends to provide demographic targeting and may provide relatively good traffic data on sites. It’s intended for media planners, while Google’s new and improved Trends is for the general public.
As I’ve tried to argue, when local targeting improves (by zip, neighborhood) and US Census and other information are layered on top of that, you have a potentially much more powerful demographic targeting tool: