Google Ad Planner
is a helpful free tool from Google that allows you to easily identify websites are the most likely to attract your target audience and is especially useful when you plan to purchase advertising or banner ad space on other websites.
My first online marketing related job was as an Online Media Buyer position and what I did was manually find websites that would be ideal to put banner ads on; scour the search engines using certain keywords and make an extensive list on a spreadsheet with all the sites and their Alexa rankings; note what type of ads they had and their sizes and locations on a page; then contact and negotiate rates. Part of the correspondence involved asking them about their traffic, getting information about their visitors such as demographics. Sometimes you get glossed up information, that you would be unable to verify. It would have been good at the time to have another website that had data on a website’s traffic.
Today, Google Ad Planner makes research easier. It enables you to define audiences by demographics and interests and through that information, create media plans that would reflect your audience’s online behavior and identify the right websites to place his/her advertisements.
Here is a video that gives you a quick overview of Google Ad Planner.