Subjects of historical study today include:
Melungeons
Various "No Man's Land" spaces in America, including the Neutral Ground between Louisiana and Texas, and the Cimmaron Territory of the Oklahoma Panhandle. Wacky, lawless historical stuff!
Various aspects of Romany/Gypsy culture including:
Famous people with Rom blood (Michael Caine - Irish Traveler actually, which is different), Bob Hoskins and (they think) Charlie Chaplin. Rom claims on Elvis seem specious. (But that's what lead me to Melungeons, aka "Black Dutch".)
The close relationship between Romany Law and Orthodox Jewish Law. (It's extremely patriarchal and very restrictive for women. It's odd that the stereotype of the gypsy woman is so sensual and licentious, but that's completely the opposite of her status in Rom culture where she's expected to be virginal at marriage and any indication to the contrary would make her unmarriageable.)
I just read the book Gypsy Boy the other day and I'm trying to place his personal experience within the larger context. It's a fascinating book, btw, and a big bestseller in England. It's been optioned for a movie and he's got a sequel out (about his life on the run from his Gypsy father as a teenager. He came out as gay and ran off with a man. So his father put out a "blood avenger" hit on him and the guy.)
I hadn't realized there was so much enmity between Irish Travelers and British gypsies. (The British gypsies who claim Romany connection still self describe as "gypsy" though they are properly called Romanichel. Welsh and Scottish Rom are distinct and have their own culture/customs.)