Hex has recently been added to the Polish game server Kurnik. You can get English menus if you click on the British flag in the top right corner. They offer 10x10 only, and Net lag can eat up your clock time, but there are some strong players there. Ratings and ladder rankings are implemented.

Of course the most popular Realtime server remains Playsite. Board sizes 10x10, 14x14, and 18x18. A single rating system applies to all three board sizes.

There is also the Spanish server Ludoteka, with menus available in Spanish, English, French, or Basque. 11x11 only. No ratings.

Last and least is Jatek, which is in Hungarian only, and almost no one plays there. Some of the strongest Hex players I have known are Hungarian, but their server is the pits. They call Hex “Híd” for some reason, if you want to try it our for yourself. Board sizes 8x8, 10x10, and 12x12. You wager as many of your rating points as you wish, which is a bizarre workaround for not knowing the rating formula.

Sadly, the best Hex server ever, Newton games, is offline, apparently a victim of catch-22.