This doesn't just apply for podcasting, but I recommend a good "Responsive" theme that meets accessibility standards with 2 columns, one for content and the other for the sidebar.
Reasons:
* Content is king, so keep your sidebar to a minimum.
* Responsive theme means you no longer need to worry about providing a mobile version of your site.
* Accessible sites not only help those who are visually impaired, but they also happen to be perfect for SEO.
Audio podcasts and regular blog themes work great.
Video podcasts though can take advantage to having a custom theme developed specifically for what you're trying to distribute. Check out the
www.tpn.tv theme we custom made for that site, it features a heading across the top of the 4 most recent video episodes with their poster artwork.