There quite a few podcasts covering the topics of illustration and comic book art.
A couple of my favorites are Sidebar Nation and Ninja Mountain.
Sidebar Nation, http://www.sidebarnation.com/, is hosted by Dwight and Swain, two thoroughly knowledgeable guys who have a deep love of comics from way back in the day. There podcasts are interviews with a who's who of comics, graphic novels, concept art and illustration. This week, for their 101st episode, they interview the incredible Greg Manchess.
Ninja Mountain, http://ninjamountain.blogspot.com/, a loose collective of illustrators discussing all the nuts and bolts of illustrating sci-fi/fantasy. The podcasts is always interesting. As a group they are in different stages in their careers so the podcasts give you a broad down-to-earth view of the topics.
Both these podcasts are available at their blogs and through iTunes.