Clubs are on Star Stable E V E R Y WHERE! Of course, I know 2 clubs in English servers. 

1. Mystery Riders (English Server)

2. Frosty Queens (English Server)

(This are NL clubs btw.)

1. Frost Arrows Inc. (MM)

2. Doyles Wolves Legacy (MM)

3. Royal Roses Army (Royal Roses Agency) (MM)

4. Glorious Winners (SM)

5. Rain Kings (HH)

6. Crystal Roses (SM)

7. The Agents Generation (MM)

8. Zany Bears (MM)

9. Zany Heroes (HH)

10. Pink Star Squad (MM)

11. Zany Riders (MM)

12. Zany Stars (MM)

13. Money Wolves (MM)

14. Frosty Forest (HH)

15. Wednesday Mustangs (MM)

16. The Jokers Agency (MM)

17. Thunder Hooves Army (MM)

18. Great Dancers (MM)

19. Zany Queens (MM)

20. Frosty Stars (MM)

21. Awesome Turtles Family (MM)

22. Elite Roses Club (MM)

23. Trotting Hooves Inc. (MM)

This are all clubs I know! Sorry if I forgot you ;-; I forgot some clubnames..