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 271,724 websites that are Alexa Certified Site Metrics Customers. We know of 18,663 live websites using Alexa Certified Site Metrics and an additional 253,061 sites that used Alexa Certified Site Metrics historically and 6,246 websites in the United States.
Get a list of 271,724 websites using Alexa Certified Site Metrics which includes location information, hosting data, contact details, 18,663 currently live websites and an additional 35,605 domains that redirect to sites in this list. 253,061 sites that used this technology previouslyand 6,246 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.