Google Ad Planner, a free media measurement tool

For all you media planners out there, you’ll get a kick out of this free tool; Google Ad Planner. It can help you narrow down what websites your audience is more likely to visit and therefore, help you make better informed advertising decisions. The whole idea is to help us discover relevant sites for your products and services.
With this great free tool you can:
– Find websites relevant to your audience, create lists and store them in a media plan
– Define audiences interests and demographics
– View the number of unique visitors, page views, and other data for millions of websites from over 40 countries
– Generate aggregated website statistics for your media plan

When google announced this tool it was only available by invitation only but now is available to anyone with a Google account.