A growing number of Americans are listening to podcasts, but very few do so every day.

The Pew Internet and American Life Project said Wednesday that 12 percent of Internet users have downloaded a podcast, an increase from 7 percent earlier in the year.

However, only about 1 percent said they download a podcast on a typical day -- unchanged from the survey earlier this year. The rest do so less frequently, perhaps only once.

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While podcast downloading is still an emerging activity primarily enjoyed by early adopters, the range of content now available speaks to both mainstream and niche audiences," said Mary Madden, senior research specialist at Pew. "We are at a crossroads of a major transition in the way media content is delivered and consumed."

The array of individuals and mainstream media institutions that now provide podcasts has also expanded dramatically. For example, in November of 2004, Podcast Alley, a podcast directory website, listed fewer than 1,000 podcasts for download. Today Podcast Alley catalogs more than 26,000 different podcasts, totaling more than 1 million episodes. In addition to homegrown podcasts that cover topics ranging from music and fashion to religion and politics, mainstream media institutions such as NPR, the BBC and Comedy Central now regularly provide podcasted material as an alternative way to distribute their content.

I created a domain name a few years ago, www.podosphere.com, thinking I might do something with it. I've decided that I won't be, so I thought I would auction it off. Someone out there is planning yet-another-podcasting-aggregation site, I bet.

Our survey showed that only 1% of online households in North America regularly download and listen to podcasts. And when you include all of the people who are just interested or have used podcasts, they strongly favor listening to existing content like Internet radio or broadcast radio, not necessarily new content. (And for newspapers thinking about podcasting, putting print stories into audio format just ranked ahead of original content from bloggers) I think this has something to do with 1) original content just isn't as well known; and 2) existing content benefits from users that simply want to time shift it. (Shameless plug: there's lots of other demographic and measurement data about podcasting in the brief).

Advertising on podcasts, which are invariably free to the end user, is in its infancy to put it mildly," says Mr. Chapman. "However, the nature of the audience and strong growth in its numbers have already driven major brands to invest in podcast-based promotion. More advertising and sponsorship will inevitably follow, as evidenced by the sprouting up of several companies dedicated to facilitating podcast advertising and measuring its effectiveness."

In their pursuit of venues that deliver a measurable, targeted audience, online advertisers and marketers are paying serious attention to this new "anywhere, anytime" channel.

Gervais' podcast also features his "Office" co-writer Stephen Merchant and their former radio producer Karl Pilkington, as the trio take on a succession of offbeat topics from vampires to a regular segment called "Monkey News."

The free half-hour show -- essentially a radio program that can be downloaded to a computer or portable audio player -- now occupies the top spot on the podcast charts of the U.S. and UK iTunes Music Stores run by Apple Computer, whose popular iPod digital music player was the basis for the podcast name.

General Motors Corp., credited as one of the first corporate podcasters when it dipped its toe into the waters in February, records talk-radio-style episodes about its vehicles that were downloaded 75,000 times in August. Disneyland celebrated its 50th anniversary in May with a series recorded inside the park. Verizon Wireless issued one a few days ago to promote a cell phone that will, among other features, let you listen to podcasts.

International Business Machines Corp., which produces podcasts for investors about the future of trends, also set up a podcast-recording system for employee communication. And many media companies, from the BBC to ESPN to The Sun, have jumped on board for simple self-preservation.

"Companies are completely losing control of their messages, and the one way to get into the game is by blogging and podcasting," said Michael Wiley, GM's director of new media. "The companies that are early adopters stand tremendous opportunity to be the winners in the long run."

It’s a rendered OPML file, which is a bit different from an ordinary web page. Visually, this list looks like a series of nested outline item. (You'll probably see a folder icon displayed to the left of each item.) Wherever you see a "+" mark next to an item, click on that to expand the view to see what's inside. Similarly, a "-" mark indicates that you can collapse that item, or that the item cannot be expanded further.

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.

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

"I think there is a lot of money to be made out of this, but it's in its infancy," said Mark Vavrick of Renegades of Comedy. "There's a lot of people with computers, but not everybody knows these shows are out there yet."

"I have 50, 60, 70,000 listeners. I could make a couple of bucks off that, but not much. If you are talking a million podcasters, and then you can kind of divide that amongst ourselves, then that is kind of interesting."

Essentially, he says, if you are doing a bass fishing podcast, someone who is selling bait and tackle will probably want to advertise on your show.

He is clear the ads will not be the traditional "in-your-face" type familiar to commercial radio now.

"We are really going to see these microcosms and commerce will be all over the place."