WP Super Cache is a page cache generation tool for WordPress.
http://wordpress.org/extend/plugins/wp-super-cache/
Widgets · WordPress Plugins
Get access to data on 3,632,005 websites that are WP Super Cache Customers. We know of 1,081,598 live websites using WP Super Cache and an additional 2,550,407 sites that used WP Super Cache historically and 584,714 websites in the United States.
Get a list of 3,632,005 websites using WP Super Cache which includes location information, hosting data, contact details, 1,081,598 currently live websites and an additional 431,331 domains that redirect to sites in this list. 2,550,407 sites that used this technology previously and 584,714 websites in the United States currently using WP Super Cache.