Krafty Librarian has done a great job of compiling a complete list of the medical podcasts in a downloadable MS Word file:http://www.kraftweb.net/kl/podcasts2.doc
"I have sifted through a lot of web sites, lists, and iTunes programs.
Please feel free to suggest any that I am missing.
As this list grows it may be necessary to create two lists: those for consumers and those for medical professionals."
UBC Google Scholar Blog features the Top Five Podcasting Articles in Medicine (March 2006).
Update 3/28/06:
Krafty Librarian has updated the list of medical podcasts:
"When I first started on this endeavor I found eight podcasts, five months later the list grew to 34 podcasts, seven weeks later I have a list of 52 podcasts."
Update 06/16/2007: More links
Podcasts and Videocasts. UBC Health Library Wiki.
Podcasts and vodcasts in medicine. Dean Giustini (PDF)