As Karla Gilbert walked through a California airport last fall, three men stared and began to whisper. She didn't know them, but they knew her.

Gilbert had similar moments all weekend as she attended the Portable Media Expo & Podcasting Conference. Strangers knew her from the video podcast she started because she didn't have a hobby.

"It is becoming a lot more than a hobby," said Gilbert, who lives in Portland.

Gilbert's "Rumor Girls," and its predecessor "The Mary and Karla Show," rank among the top comedy podcasts on Apple's iTunes Music Store, a popular Web site to download music, videos and programs. A San Francisco-based company is negotiating to put Gilbert's podcast on its online network and add advertising.

Thousands of people get an episode of "Rumor Girls" downloaded on their computers weekly for free. They watch Gilbert and her sister, Karen Gilbert, chat about men, going out at night and friends at different locations in Portland.

"For us, it's just everyday life," said Karen Gilbert, who owns an Auburn-based graphic design firm, Gilbert Creative Design.

The show thrives on the rising popularity of video podcasts and the sisters' hard work cultivating a fan base. The Gilberts spend hours on the Internet each week chatting with their fans, returning e-mails and updating an account on MySpace.com, a social networking Web site.

The weekly, 10- to 20-minute show is mostly ad-libbed. Franklin McMahon, Karla Gilbert's boyfriend, shoots it on a small, handheld, digital camera. Patrons at a coffee shop where "Rumor Girls" filmed recently may not have known they were in the podcast.

Those involved with the show don't give out the number of subscribers, but McMahon says it is "multiple thousands" and they stretch to Finland, Italy and Japan.

"There are people obsessed with the shows," said McMahon, owner of a Portland-based media company, Franklin McMahon Studio.

The appeal of first "The Mary and Karla Show" and then "Rumor Girls" is similar to reality television. It is intimate, unscripted and a portal into the lives of others. McMahon says much of the shows' foreign audience are just interested in how American women live and what they talk about.

"Like reality TV, you are really intrigued with these people's lives and tune in," he said.

But success in the podcasting world can create a split reality for those involved. Karla Gilbert, who works as a hair stylist, finds many of her clients don't know what a podcast is – let alone how to subscribe to "Rumor Girls."

For those trapped in 2005, a podcast is an audio or video program people subscribe to through their computers. Each time a new episode comes out, a digital file gets downloaded onto the subscriber's computer. Then, that person can play the file on a computer or portable device like an iPod.

Computer-users have thousands of podcasts to choose from. They range from ESPN broadcasters talking about sports, to teenagers discussing heavy metal albums.

The computer formats for audio and video files aren't new, but recent changes in their delivery has pushed podcasting into the mainstream, said James McQuivey, an assistant professor of communications at Boston University.

The iPod and other players allow people to take podcasts anywhere, and the creation of a subscription system makes it easy to deliver episodes to fans, McQuivey said.

Podcasting has drawn the interest of national television networks, popular radio shows and cable channels. But the technology remains simple and accessible, allowing anyone with a computer to produce and distribute a show through the Web, McQuivey said.

A quick search on such sites as Podcastalley.com and Podcastpickle.com show Mainers are producing casts on a variety of subjects. Most are audio and not video. The subjects include politics, music and the church sermons of a pastor in Biddeford.

Jessica Harvey of Bucksport started an audio podcast recently on home schooling, cooking and other at-home activities. She got started for less than $30, using free software and a cheap microphone connected to her home computer.

"The Mary and Karla Show" started at home as well. Karla Gilbert was timid during that first session last summer, McMahon remembers, unsure of what to say into the microphone.

But soon she and her co-star were developing different bits for their show. The show developed a following. The directory of podcasts on iTunes started to feature it. McMahon switched to video last September as Apple launched the video iPod.

The show drew the attention of PodShow, a San Francisco-based company founded by Adam Curry, a former VJ on MTV who is a leader in podcasting. The company's goal is to create a podcast network, kind of like an NBC or CBS online, where its casters can make money off what they produce, McMahon said.

Earlier this year, "The Mary and Karla Show" came to a close. Gilbert became more serious about podcasting, while her co-star viewed it as a hobby.

Now the Gilbert sisters are negotiating with PodShow and working on turning "Rumor Girls" into something more. They don't plan to quit their jobs, but they see podcasting becoming a part-time profession with sponsorships and paychecks.

"That is where we are hoping it goes," Karen Gilbert said.

Staff Writer Mark Peters can be contacted at 791-6325 or at: mpeters@pressherald.com