Pick your passion: birding, comics, cooking, digital marketing, obscure tales about Hollywood heartthrobs.

No matter the choice, there’s a podcast for you. Actually, there are probably a dozen podcasts for you. The medium, old by Internet standards, is surging in popularity.

If you’re not already listening, this might come as news to you. Podcasts — audio files available on the Internet — may seem like a relic from the turn of the 21st century, before blazing-fast Internet made streaming video accessible with a couple of clicks. But rather than killing podcasts, mobile technology has nudged the talk-a-thons toward the mainstream with an ever-growing array of programming.

“It’s still in that weird place where people who know about [podcasts] know a lot about them,” said Levi Weinhagen, who produces multiple local podcasts. “And there are people who don’t know about them at all.”

But the audience keeps growing. By one estimate, 39 million Americans have listened to a podcast in the past month, up 25 percent from the year before. Apple’s iTunes store counts more than 1 billion podcast subscriptions.

“For audiences, it’s a really exciting time because you are able to find so much stuff,” said Steve Nelson, program director at Infinite Guest, a new podcast network launched in August by St. Paul-based American Public Media.

We’re living in “an on-demand culture,” Nelson said, and “podcasts are basically the on-demand of radio.”

Emerging by app

Podcasts have been around for about a decade, so-named for the iPod. But it took some determination and tech know-how to consume them. Listeners had to find them online, download them to a computer, then transfer them to a mobile device if they wanted to listen on the go.

Podcast apps, such as Stitcher and Agogo, have made the listening life much easier. There are hundreds of thousands within iTunes — mostly for free — and all it takes is a tap to play. Fans can subscribe to their favorite podcasts, triggering automatic downloads of the newest episodes, direct to their smartphones and tablets.

The rise in popularity has lured more traditional media types into podcasting.

Locally, longtime KQRS (92.5 FM) radio host Tom Barnard left that century-old medium for podcasting. Sports talk radio station KFAN (100.3 FM) offers many of its shows as podcasts. Polished public radio shows packaged as podcasts — “This American Life,” “Marketplace,” “Radiolab” — dominate popularity rankings on Stitcher, the podcast app.

But podcasts seem to be having the last laugh in the comedy niche.

Comedians Ricky Gervais, Adam Corolla and Marc Maron have become superstars in the podcast universe. Maron’s show, “WTF With Marc Maron,” on which he interviews other comedians, draws millions of listeners who want to hear him chat with heavyweights, including the late Robin Williams, as well as up-and-comers such as Twin Cities-based Mary Mack.

“He does it very much radio style and high quality,” said Mack of Maron.

She confesses she wasn’t aware of the podcast’s popularity until new fans started driving hours to her live shows, saying they had heard her on “WTF.” She doesn’t listen to many podcasts herself, because some hosts are too interested in self-promotion or shows have low production quality.

Yet that low-budget creativity is a draw for many podcast listeners as well as the hobbyists who produce independent shows.

“Part of what people like is there’s this sort of indie band garage aesthetic to it. You’re getting something slightly rougher,” said Bill Stiteler, of Minneapolis. He contributes to multiple podcasts, including “Birdchick” with his wife, Sharon, and “Brandi and Bill Talk About Blaxploitation” with comedian Brandi Brown, in which they discuss the 1970s subgenre of action-oriented African-American films.

Listeners also develop a personal connection with hosts.

“People are drawn to [podcasts] because they might actually know a podcaster, as opposed to having information handed down from this big amorphous media conglomerate,” said Melissa Kaercher, of Robbinsdale, who co-hosts the Xanadu Cinema Pleasure Dome movie podcast with her friend Windy Bowlsby.

Recording fun

Even discussions about making podcasts draw listeners, as evidenced by the quick rise of “StartUp,” a top-ranked podcast about launching a podcast network by former public radio producers.

Nelson, of American Public Media’s Infinite Guest network, said the push into podcasting with existing radio shows and new Internet-only shows reaches a younger, more diverse audience. Some people like “buddy podcasts” with two or more hosts chatting about a topic, while others want storytelling.

One of the network’s new buzzed-about additions is Karina Longworth’s “You Must Remember This.” Like many podcasters, she came up with an idea — researching and telling stories about forgotten Hollywood histories — and taught herself basic recording and editing through tutorials she found online. Then she put it on the Internet. A few months later, she had 9,000 to 10,000 regular listeners when she joined Infinite Guest.

“It’s kind of a magical happy accident that other people liked it,” she said.

While Longworth’s homemade podcast seems poised for the big time, there are plenty of local hobbyists who record shows simply because they can. All a person needs is a microphone and an Internet connection.

“It’s never been easier to get a podcast onto iTunes,” said Kevin Hunt, social media manager at General Mills, who records the “Talking Points” podcast about digital marketing each week with Minneapolis public relations professional Arik Hanson.

As co-host of “The Wayne Gale Variety Hour” podcast, Danno Klonowski doesn’t have a huge following, maybe only a couple hundred listeners. (The name refers to a character in Oliver Stone’s 1994 film “Natural Born Killers.”) Klonowski, of Minneapolis, simply enjoys making the show, riffing on pop culture with friends and having an excuse to talk to interesting people.

He recently scored an interview with veteran Hollywood actor Tom Sizemore by working his social media connections.

“I was really nervous at first,” Klonowski said. But after the two-hour interview, “I felt like a real talk-show host.”