Consider the vast variety of approaches that have cropped up since Apple's iTunes upgrade this summer started delivering thousands of new listeners to podcasters who once toiled in obscurity.

GrapeRadio podcaster Brian Clark is now gulping down about $1,000 a week from sponsors of his show for wine hobbyists. Grant Baciocco of the fiction serial The Radio Adventures of Dr. Floyd sells show-themed buttons and T-shirts and offers guest-voice roles for $50.

Josh of Josh in Japan is asking for PayPal donations from fans of his tales of expatriate life, though so far only $14 has rolled in. And Jimmy Diggs uses his Vegas-based Daily Noise as a traffic generator for his internet radio site, LVRocks.com, where sponsors pay for banner ads. (Editor's note: LVRocks.com hosts the author's podcast, Vegas S&M)

"There isn't much information out there on how to do this," said Tim Bourquin, producer of the sports-themed Endurance Radio podcast. "It's a work in progress, how this all works."

Endurance Radio was sponsored for a time by Gatorade and is now carrying ads from Fleet Feet Sports, a chain of running-shoe stores. Buoyed by their success, Bourquin and his brother Emile now offer tips on how to profit from podcasting on their weekly Podcast Brothers show, and their website provides a boilerplate contract for podcasters to use with advertisers. Bourquin is also organizing the Portable Media Expo in November in Ontario, California, to teach other podcasters how to "monetize" their shows.

One of the biggest challenges, says Bourquin, is that most potential sponsors don't even know what a podcast is.

"I've learned not to go in and say, 'We have a podcast and you should advertise,' because their eyes will glaze over," said Bourquin. "Instead, say, 'We've got this online radio program.' It's not quite correct, but people understand that a little better. And then you tell them the neat thing is that people can get the show automatically downloaded onto their MP3 player."

In addition to polishing their pitches to advertisers, podcasters are experimenting with different business models. Some are considering offering part of the podcast for free and the rest for a fee. Others hope that a network will buy their shows for syndication on broadcast or satellite radio, thereby plucking them out of the podosphere altogether.

Diggs, of LVRocks.com, says advertisers are more persuaded when he tells them the site is getting more than 1 million hits a month than if he tries to estimate the number of unknown listeners downloading the shows he broadcasts. But some of the podcasters he hosts are finding success in getting commercial radio-show-style sponsors, including Renegades of Comedy, which landed an ad from the Vegas strip joint Cheetahs.

By and large, though, local business sponsorships don't work well, as Sam Hallgren and Adam Kempenaar of the breakout hit podcast Cinecast discovered when they landed ChicagoMixer.com as their first advertiser. The site, a dating service for Windy City singles, saw little increased traffic for its money, and Cinecast is now sponsored by DVD vendor MoviePassions.com, a more logical and less geographically dependant fit.

"Twenty percent of our listeners are from 59 other countries, so something specific to one location didn't turn out to be the best sponsor for us," Kempenaar said. "I wasn't really surprised, but this is new, so it's all trial and error."

With so much uncertainty surrounding the format, it's perhaps no surprise that few major companies have jumped into the podcast sponsorship game so far, and those that have are supporting tried-and-true news and entertainment providers. Z100, the New York radio station, signed Virgin Mobile for commercials on its podcasts of comedy bits and interviews from its morning show. ABC News has Verizon Online USA on board for podcasts of the audio of Nightline. And Slate had Chrysler plugging cars at the top of its daily podcast, in which editor Andy Bowers reads a story from the site.

"Chrysler was excited about supporting this new technology and being identified with Slate's launch of it," said Slate publisher Cliff Sloan in an e-mail. "Chrysler ran other ad campaigns on Slate at the same time. In general, we're finding that advertisers are looking for new and different ways to reach people."

Other brand-name podcasters see the podcast itself as the advertisement. Fox Entertainment produces a weekly two-minute podcast that that does nothing but promote upcoming episodes of The Simpsons and Family Guy and yet often tops the iTunes charts. And Bravo has created podcasts featuring comic Kathy Griffin of My Life on the D List and the stars of Queer Eye For the Straight Guy that encourage listeners to watch those shows.

"It's an informational tool that extends our brand and our reach," said Frances Berwick, Bravo senior vice president for programming and production. "It's another way of enhancing the viewer experience. Our viewers tend to be upscale and early adopters of new technology."

Independent podcasters don't have the assurance of a built-in audience whose demographics they can rely upon. In fact, they struggle to even accurately count the size or makeup of their audiences -- information that advertisers covet. Some have rough ideas based on e-mail responses, site hits and, if they're lucky, download figures, but they say they can't tell how many people are listening through Apple's iTunes service, which doesn't share its statistics.

That's frustrating for folks like Cinecast's Hallgren and Kempenaar, whose show has been featured a couple of times on iTunes' homepage. The duo believe that iTunes is caching Cinecast on Apple's servers, and while they're grateful for the attention, they say that as a result users who subscribe to the podcast aren't downloading the program from the Cinecast server, making it impossible to accurately count the audience.

Denver-based Barefoot Radio co-host Paul Saurini, who is trying to gauge listener demographics through an online survey, is similarly delighted by the exposure Apple provides, but frustrated by the company's coyness.

"I'd even pay iTunes if they'd share the stats with me," said Saurini, 31, a self-described former stoner who chats about weird news items and plays music on his podcast. "I would love to learn how can I take advantage of their system better so I can get more listeners. They should realize that indie podcasters would pay for that information."

Even an appearance on the iTunes Top 25 podcast list or Top 100 download chart doesn't provide a solid metric, because Apple is mum on how the rankings are decided, and discrepancies between the two lists have gone unexplained. An Apple spokeswoman declined to comment for this report, and specifically refused to answer questions about the ranking system.

That leaves many would-be podcasting entrepreneurs on shifting ground.

Saurini, who plans to attend the Portable Media Expo, says he's unsure how to approach advertisers, so he's hoping one will hear his show and decide to invest in him. But he realizes his podcast, driven largely by his and his co-host's personalities and humor, could be a harder sell than topic-specific programs focused on running or movies.

Still, the passive approach sometimes works. Tower Records, for example, surveyed the podosphere for music-related podcasts they could sponsor and settled on two, Coverville and The Nashville Nobody Knows, for their first ventures. The selection came out of the blue for those podcasters.

"Basically, we love podcasting," said Tower marketing vice president Mike Jansta in an e-mail. "We were looking for a way to associate Tower Records with some of the unique and high-quality podcasts that are out there.... Coverville and The Nashville Nobody Knows were two podcasts that really stood out to us. The quality of the commentary and content of both are fabulous."

Many early podcasters say they're in it for the long haul and expect profits to come later.