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 3,714,637 websites that are WP Super Cache Customers. We know of 1,191,881 live websites using WP Super Cache and an additional 2,522,756 sites that used WP Super Cache historically and 626,408 websites in the United States.
Get a list of 3,714,637 websites using WP Super Cache which includes location information, hosting data, contact details, 1,191,881 currently live websites and an additional 382,628 domains that redirect to sites in this list. 2,522,756 sites that used this technology previously and 626,408 websites in the United States currently using WP Super Cache.