I suspect something like this may have been done before, but I failed to find it search. Somebody noted a theme where a few cards with similar names do similar things. I wondered how many more themes are out there that I haven't recognized. Here's what I have so far, with (?) marking those that are a bit of a stretch:
Church (trashing): Chapel, Bishop, Altar, Temple, Tomb (?)
Town (+2 actions): Village, Shanty Town, Mining Village, Native Village, Fishing Village, University (?), Worker's Village, City, Farming Village, Hamlet, Border Village, Inn (?), Fortress (?), Bandit Camp, Plaza (?), Port (?), Lost City, City Quarter, Bustling Village, Villa
Sellers (a little of everything): Market, Grand Market, Peddler, Market Square, Farmers' Market
Horror (cards back on the deck): Ghost Ship, Haunted Woods, Haunted Castle
Royal Settings (repeated actions): Throne Room, King's Court, Procession, Crown, Royal Carriage
Travel (discounts): Bridge, Highway, Bridge Troll, Ferry
Witch (curses): Witch, Young Witch, Sea Hag, Swamp Hag
Iron (cantrip + variable bonus): Ironworks, Ironmonger
Real Estate (victory cards): pretty much all the victory cards except Harem, Nobles, and Dame Josephine)
Storage Rooms (discard/sifters): Cellar, Vault, Warehouse, Catacombs, Stables, Storeroom, Dungeon, Secret Chamber
Wisemen/Wisewomen (sifters): Sage, Scrying Pool, Apothecary, Cartographer, Jack of All Trades, Spy, Navigator, Oracle
Diplomacy (draw + benefit to/involvement of others): Council Room, Embassy, Envoy, Advisor?
Trade (Silver): Trading Post, Trader, Trade
Wilderness (Draw): Hunting Grounds, Ranger, Scout, Guide?, Pathfinding
Blacksmithing (Draw): Smithy, Royal Blacksmith
What have I missed? What have I mis-categorized?
Edited to update the input from others.