In a report on podcasting to be published today, RSS feed management company FeedBurner say that their service is now managing just under 45,000 podcast feeds.

Contrast this number with the 6,000 podcast feeds the company was managing at the time of its last report in May 2005. According to FeedBurner’s data, this remarkable latest figure represents an average growth rate of 15% month over month, and exceeds the total number of radio stations worldwide.

Rich media feeds (podcasts and videocasts) represent just under 20% of the quarter-million RSS feeds managed by FeedBurner, who say that it has more than 1.6 million aggregate subscribers to FeedBurner-managed podcasts, a number that has more than doubled in the past six months. Their data indicates that people are subscribing to rich media feeds at a rate that outpaces general RSS feed subscriptions by about 40%.

FeedBurner’s report also says that podcast directories are growing and driving activity back to the podcasters’ originating website. This reflects what happens with text feeds (eg, blog posts and other website text content) where RSS distribution begins as a mechanism to drive traffic to the originating site and then evolves to become its own consumption medium.

While a number of reports have been published in recent months about projected growth of podcasting – some even predicting a slowdown – and podcast listenership, this is the first hard evidence to compare numbers over a near-12-month period.

It clearly shows that growth in podcasting is continuing and is consistent. Indeed, the growth in podcasting looks like it’s running parallel to the continuing growth of the blogosphere.

(I saw a pre-release version of FeedBurner’s report. I’ll update this post with a link to the report when it’s available. 18/4 @ 19:00 CET: FeedBurner have just posted the report on the FeedBurner blog – Expanding Universe: Podcasting Market Update.)