Today, Google announced Google Ad Planner, taking a direct shot at services offered by comScore and Nielsen. Differing from Google Trends for Websites, Ad Planner is aimed at media buyers looking to identify target sites for ad placements. In a market where Nielsen and comScore charge hefty sums to advertisers for access to their data while at the same time being loathed by publishers for the inaccuracies of their panel based measurement systems, Ad Planner is likely to gain acceptance fairly quickly.
There is also a level of integration with DoubleClick's MediaVisor product. The possibilities for integration between the DoubleClick and Ad Planner are endless and will give Ad Planner a distinct advantage over competing services. The service is currently in closed Beta right now but I'm hoping to get my hands on a login so I can test it out.

