@haubles @bmann @mozilla @medium Flipboard and Vivaldi also have servers
For cities, I think Amsterdam is the biggest city with their own servers that I know of. Obviously EU Voice is massive, as well as bund.de.
Another very big project is with the Dutch higher education system, where they enable all Dutch universities to join the Mastodon server. Think 25 have signed up now in the roughly month since it launched. Did an interview with the PM on that here https://fediversereport.com/surf-program-manager-talks-about-their-mastodon-pilot-for-dutch-higher-education/