Podcasts, the once-buzzed-about medium has spent the past two years building its audience and enhancing ad capability, though advertisers still remain skittish due to the newness of the medium, writes Business Week.

Nevertheless, the medium's adoption by major players like CBS Radio and Rush Limbaugh show that it has crossed over into the mainstream. Also attractive to advertisers is the highly targeted audience of many podcasts. For example, there are podcasts for those interested in consumer electronics, skateboarding, comic books and scores of other niches.

"You can really serve a niche much better than traditional television," says David Prager, chief operating officer and VP of programming at Revision3, an online television network that shows video podcasts. Its most popular, Diggnation, is viewed 250,000 times per week, Prager says.

With eMarketer saying advertisers will spend more than $400 million on podcasting by 2011, up from $80 million last year, and an expected entrance of keyword-powered Google audio ads, podcasting is poised to take off.

Disinclined to wait for Google waiting for Google, this week Podtrac unveiled a free online service that enables advertisers to research audience info for audio and video podcasts based on demo, size and other characteristics.