Jungle Cruise- every Disneyland/MK park (I believe?) Yes, retconned to be created by Dr. Albert Falls and run by his Grandaughter, Alberta.
The Adventurer's Club- (now closed) WDW Yes, founded by S.E.A. member Colonel Critchlow Suchbench. Unclear if other members were also in S.E.A., seems to have possibly disbanded before the founding of the club. They also retconned a portrait that used to be in the Library of the Imagineers that built the Club, as members of an unscrupulous Plunderers Club, including Harrison Hightower (Joe Rodhe).
The Explorer's Club - HKDL Yes
Mystic Manor- HKDL Yes, both Lord Henry Mystic and Albert the Monkey are members
Mysterious Island- TDS ? I think anything Nemo is tangentially related, but I doubt Nemo was a member. Doesn't seem like a "joiner"
Fortress Explorations - TDS Yes, the builders of the Fortress seem to be the founders of the earliest version of S.E.A.
Tower of Terror- TDS (Harrison Hightower) Yes
Skipper Canteen- WDW Yes
Captain Nemo (20,000 leagues) walkthrough area - DLP (I haven't been there) See above.
Big Thunder (DL and MK only?) - Owner Barnabus T. Bullion is a member.
Oceaneer Lab (Cruise Line) - Captain Mary Oceaneer and Salty the Parrot
Miss Fortune Falls - Also Mary and Salty
Jock Lindsey's - Jock is a member, unclear if Indy is too. Maybe not, he's also not really a "joiner". Still, same universe, so anything Indy is also in.
The Lamented Unbuilt Discovery Bay - Jason Chandler was a character worked into the backstory of Big Thunder who would've gone on to found Discovery Bay. He is a member, and many references are also made to him owning the Hyperion airship, and maybe the Nautilus after Nemo?
Adventureland Trading Company - Involved in the two or three games Imagineers conducted that involved scavenger hunts to collect Juju artifacts. Apparently the Jujus were shipped from Mystic's collection originally.
The Museum of the Weird - A Madame Zasher is referenced in a letter from Jason Chandler
Haunted Mansion - One of Constance's ill-fated grooms was George Hightower, presumably a relative of Harrison
Raging Spirits - Harrison stole artifacts from the site.
Adventure Isle - I'm unclear if the fictional group running the dig site at Raging Mountain is related or not.
Journey Into Imagination - Dreamfinder makes a cameo at the Skipper Canteen
Pleasure Island (R.I.P.) - Merryweather Adam Pleasure was a member.
Typhoon Lagoon and Stormalong Bay - Since Pleasure's whole backstory has been adopted in, the typhoon he was lost in is cannon, and I believe that is the same storm that wrecked the ship at Beach Club and created Typhoon Lagoon. I think they're also tying the storm into Miss Fortune Falls' backstory. Someday it would be interesting for WDI to explore the mystery of why so many calamities have befallen S.E.A. Members.
Wilderness Explorers - I feel like there is a reference to them, but I may be mistaken. I do have a headcannon that I like that Emil Bleehall of the Adventurers Club went on to found the Wilderness Explorers, wish it were true.
I think that's it, everything's so interconnected that it's like a puzzle, with scraps and clues scattered all over.
