PrivacyChoice
privacychoice.org
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
PrivacyChoice maintains a comprehensive database of tracking companies, including domains used by over 450 ad and data companies, their privacy policies and opt-out and opt-in processes. By continuously scanning top websites and collecting information from a panel of users, PrivacyChoice maintains a map of the companies collecting data on popular websites. We use this to identify new trackers and to verify opt-out effectiveness.