NEW YORK (AP) — Sex toys. French films. Star Wars action figures. Erotic photos.

What do these things have in common? They’re the gifts that keep on giving — about every month.

Dozens of online subscription businesses have popped up offering to ship boxes of different goodies within a given niche or theme, like makeup or travel, each month. Most often, the exact products remain a mystery until they’re shipped.

These monthly subscriber services have gained fans among those who appreciate novelty and surprise. But as their popularity has grown, the list of products they offer has gone from ordinary (Think: hair products) to really niche (Think: black socks) to naughty (Think: vibrators.)

Overall, subscription services account for less than one percent of the nation’s $231 billion online business, excluding the movie subscription service Netflix, Forrester Research estimates. But experts say they are poised to do well during the holiday season because there aren’t a lot of must-have gifts on people’s wish lists.

“There’s so little that’s new to buy for the holiday season,” said Candace Corlett, president of WSL Strategic Retail, a retail consultancy. “The idea of a subscription service is fun and exciting.”

Of course, shoppers have long been able to order fruit, movies or wine through monthly services. But since online subscriber service Birchbox launched surprise makeup samples in 2010, there’s been an explosion of these businesses that focus on nearly every desire imaginable.

Boinkboutique.com delivers vibrators and other sex toys and features plans like a $25 monthly “make out” box. Blacksocks.com, which has 60,000 subscribers, sends three pair of socks, including striped and colored versions, four times a year for $118 annually. And for $45 per box, Trytheworld.com ships hard-to-find food items like jams and fine teas and cultural finds from Paris, Tokyo and Rio.

Trytheworld.com, which launched in August, declined to say how many subscribers it has, but co-founder David Foult said it’s reaching customers who “love the idea of traveling and discovering new cities” but “don’t necessarily have the time or the money to do so.”

Balthazar Simoes, an erotic photographer for years, took the idea of discovery a step further with his service. For $10 a month on his website, callmebalthazar.com, “Peek in the Mail” subscribers receive two 5-by-7 inch photos of erotica.

Simoes said about a few dozen subscribers have signed up for the service since it launched last year, and he insists it’s striking a chord with voyeurs and amorous couples. “It’s a novelty to get beautiful prints in the mail,” he said.

The novelty of subscriber services, in general, are resonating with people like Moire K. Tivenan, 28, who was stumped on what to get as Christmas gifts for her family — until she found subscription services.

She wound up getting her 21-year-old brother a subscription to Birchbox for men’s grooming products like shaving cream for $20 a month. She signed up for My Ireland Box, a box of goodies and crafts from Ireland like shamrock oven gloves for a $150 three-month subscription, for her mother.

And for her 24-year old brother, she turned to Nerdblock.com, a $19.99 monthly service that sends a box of T-shirts and collectible figures from brands like Star Wars and Marvel.

“I picked something specifically geared toward their tastes,” said Tivenan, who lives in Brick, N.J. “At the same time, it’s a surprise for both of us … because neither of us knows what they’re going to send.”

Not every subscriber service is successful, though. SecretSexBox.com promised “better sex to your doorstep” for just $19.95 a month with a box of products that featured a different sexual theme. But the site’s owner called it quits in September after just over a year in business.

Turns out, the monthly subscriptions were too frequent, said founder Tom Nardone. Long-term subscribers wound up with a “nightstand full of stuff,” said Nardone on a post on the website.

“Getting a new box of sex toys and romantic gifts every month sounds like a great idea,” Nardone said. “But in practice it wasn’t.”