Survey Says

"19% - Podcasts Proliferate" the daily number at the Pew Research Center.

Excerpt:

As gadgets with digital audio capability proliferate, the number of internet users downloading podcasts has risen from 12% in August 2006 to 19% today. Still, podcasting has yet to become a fixture in the lives of internet users, as only 17% of those who have download podcasts do so on a typical day. Men are more likely than women to download podcasts, and internet users under 50 years old are significantly more likely to do so than older users. Internet users with a broadband connection and those with six years of internet experience are also significantly more likely to download podcasts.