Just announced are the Nielsen/ Net Ratings reports which sees Microsoft lead the list of Top 10 Parent Companies while Google leads the list of Top 10 Brands.
"Example: The data indicates that 45.2 million home and work Internet users visited at least one of the Wikimedia Foundation-owned sites or launched a Wikimedia Foundation-owned application during the month, and each person spent, on average, a total of 16 minutes and 35 seconds at one or more of their sites or applications.
A parent company is defined as a consolidation of multiple domains and URLs owned by a single entity. A brand is defined as a consolidation of multiple domains and URLs that has a consistent collection of branded content."
To see the entire report, view PDF file.