Don't forget to make sure the page with the podcast is accessible too...its not going to be much good if the screen reader has trouble finding the link that starts the podcast playing.. by the way a good place to test the accessibility for your site (if you don't have the link already) is Cynthia says as a designer I always check the sites I make through this first...then move on to an independent testing organisation where they are tested by real people with real disabilities. However my blog...not hosted by myself is totally inaccessible and I too have massive guilt trips about it.