4PC Correspondence - Forum based (image editing) 4pc correspondence so you can play with your own time controls and absolutely any variation that comes to your imagination.
4PC Opening Explorer - A place to explorer 4pc openings (primarily Team openings).
Bulldog Chess Players - A club for anyone who enjoys a game of Bulldog Chess.
Thought I'd make a list of Variant Clubs.
Feel free to post a description and link to your own variant club here (a link to the club, not a link to join...).
Official Clubs
Variants - The Official Variant Club
Fog of War
Bughouse
Crazyhouse
3 Check
Chess960 - Fischer Random
King of the Hill
8 Player Chess
Official 4 Player Chess Clubs
4 Player Chess
Ajedrez para 4
4PC University
4PC Custom Games
The Hyper Club