Google Tag Manager:
Google LLC is an American multinational technology company that specializes in
Internet-related services and products, which include online
advertising technologies, search engine, cloud computing.
https://www.whotracks.me/trackers/google_tag_manager.html

Gravatar:
Automattic develops publishing platforms, including the WordPress.com website and the VIP WordPress.com cloud version.
 
Facebook Connect:
Facebook Connect helps track redirects through Facebook links to find out what actions Facebook users are taking on the site.
 
Google Analytics:
Google LLC is an American multinational technology company that specializes in
Internet-related services and products, which include online
advertising technologies, search engine, cloud computing.
 
Double click:
Google LLC is an American multinational technology company that specializes in
Internet-related services and products, which include online
advertising technologies, search engine, cloud computing.