Scott Johnson, VP Eng & Co-Founder of Feedster, releases usage stats on MP3 enclosures in the RSS feeds that Feedster monitors.
The numbers are small now (35 MP3s in the last 24 hours, 696 “all time”), but given the stampede of traffic that hit my site for the Anatomy of an iPodder article (thanks to a kind link from Scoble on his link blog), interest is very strong.