Alexa's certified program and pro metrics.
http://www.alexa.com/siteowners/certify
Analytics and Tracking · Audience Measurement · Visitor Count Tracking
Get access to data on 271,038 websites that are Alexa Certified Site Metrics Customers. We know of 18,468 live websites using Alexa Certified Site Metrics and an additional 252,570 sites that used Alexa Certified Site Metrics historically and 6,136 websites in the United States.
Get a list of 271,038 websites using Alexa Certified Site Metrics which includes location information, hosting data, contact details, 18,468 currently live websites and an additional 35,194 domains that redirect to sites in this list. 252,570 sites that used this technology previouslyand 6,136 websites in the United States currently using Alexa Certified Site Metrics.
Countries
Financial
Group
Region
These are sites that we think might use Alexa Certified Site Metrics in the future because of their similarity to other sites that already do.