comScore, Inc. They do this every month, and it’s based on data from their comScore Media Metrix service. Here is the data for April 2009: Table 1 comScore Top 10 Gaining Properties by Percentage Change in Unique Visitors* (U.S.) Table 2 comScore Top 10 Gaining Site Categories* by Percentage Change in Unique Visitors (U.S.) Home, Work and University Locations Unique Visitors (000) Source: comScore Media Metrix Unique Visitors Rank Property (000) Total Internet : Total Audience 192,875 1 Google Sites 155,319 2 Yahoo! million visitors. million visitors.