Are there any really good classical podcasts?

I have found a limited number of classical related podcasts on iTunes U. You could try searching the Itunes U for Van Cliburn etc.

You mean something like this? http://www.mefeedia.com/entry/van-cliburn-treasuring-moscow-after-50-years/7304861/

or this?
http://www.mefeedia.com/entry/debussy-reverie-by-van-cliburn/6389368/

CBC Radio 2 is excellent for classical for most of the day and has some very interesting stuff on in the evenings as well. The real downside is that its streaming audio, not a podcast, and it uses windows media player. If you can bring yourself to install that then its worth checking out – all the programs on it are great. They play a lot of Shostakovitch it seems.

I probably didn’t find what you had in mind, but I want to thank you for bringing this up becasue I am really enjoying the playlist on my second link!

I like the podcast from the Isabella Stewart Gardner Museum which is mainly chamber music. It’s reliable for good pieces by well-known composers – unfortunately, it’s only updated every two weeks.