Mutter Museum

What: The most fascinating display of historical medical specimens imaginable. The collection is at once serious, comprehensive, and entertainingly gruesome.
Where: Philadelphia
How it started: The Mutter grew out of an 1850s-era collection of instructional exhibits for doctors.
Fun fact: One exhibit contains drawers full objects removed from gagging patients including collar buttons, hair clips, safety pins, diaper tabs, jacks, and skate keys.
Contact: 215-563-3737; collphyphil.org/site/mutter_museum.html
Cost: $14; $10 for minors and seniors

National Mustard Museum

What: More than 5,300 mustards, plus (wait for it!) tons of mustard-related memorabilia.
Where: Middleton, Wisconsin
How it started: “I began collecting jars of mustard on October 28, 1986, at 2:30 a.m.,” says founder Barry Levenson. “I couldn’t sleep because on the 27th the Red Sox lost the World Series. I didn’t know what to do, so I went to the grocery and just walked up and down the aisles. I had a moment in front of the mustards—and that’s how it all started.”
Fun fact: Shakespeare loved mustard. He mentions it four times in his plays. He never mentions ketchup. Not even once!
Contact: 800-438-6878; mustardmuseum.com
Cost: Free

Cockroach Hall of Fame

What: A collection of live and dead critters big enough to make your eyes bug out.
Where: Plano, Texas
How it started: Launched as a publicity stunt to attract more customers to an extermination service, the collection eventually took on a life of its own.
Fun fact: The museum is home to “Libe-roachi,” a cockroach dressed as the famously flamboyant piano player.
Contact: 912-519-7791; pestshop.com/cockroaches.html
Cost: Free

Museum of Salt and Pepper Shakers

What: More than 20,000 shakers in all. Really!
Where: Gatlinburg, Tennessee
How it started: “When I was young, my mother’s pepper mills kept breaking,” says Andrea Ludden, curator. “When one broke, she would put it on the windowsill and get a new one. As they accumulated, friends and family began to give us theirs, and the collection just grew!”
Fun fact: One salt shaker at the museum is made from the ashes of Mount St. Helens and shaped like the volcano. When you pop the top, it resembles the “after” photos.
Contact: 888-778-1802; thesaltandpeppershakermuseum.com
Cost: $3; 12 and under free

Museum of Bad Art

What: If your first thought about most modern art is: “my kid could paint that,” this place is for you. Actually, the guiding principle is: my kid did paint that—then threw it out, then someone rescued it from the trash!
Where: Three Boston-area locations.
How it started: Founder Scott Wilson actually did rescue the first painting from a trash heap one evening to salvage the frame. In a so-bad-it’s-good moment, he held onto the thing.
Fun fact: Well, everything about the museum is fun. But don’t miss the original inspiration for the collection, Wilson’s salvaged “Lucy in the Field with Flowers.”
Contact: 781-444-6757; museumofbadart.org
Cost: Free

New Orleans Historic Voodoo Museum

What: The small museum celebrates not just voodoo, but its integral connection to New Orleans.
Where: Where else? New Orleans
How it started: From a collection of memorabilia associated with Marie Laveau—the matriarch of New Orleans voodoo.
Fun fact: Contrary to popular belief, voodoo dolls were never designed to inflict pain on a practitioner’s enemies; they were used for medical record keeping. The color-coded pins let doctors know what previous ailments the patient had and how they were treated.
Contact: 504-680-0128; voodoomuseum.com
Cost: $7; $5.50 for seniors; $4.50 for high school students; $3.50 under 12

Marvin’s Marvelous Mechanical Museum

What: A 5,000-square-foot tribute to coin-operated machinery from turn-of-the-century gypsy fortune-teller machines to modern pinball games.
Where: Farmington Hills, Michigan
How it started: Museum founder Marvin Yagoda began collecting gadgets and gizmos in the 1960s. When a food court was installed in a local mall, he stuck a few of his machines in the back as a novelty. “From there, it just grew and grew and grew,” says Yagoda.
Fun fact: The first vending machine, which dispensed holy water, was invented 2,000 years ago.
Contact: 248-626-5020; marvin3m.com
Cost: Admission is free; machines cost from a quarter to $2 to operate