Radio station KCRW has a regular program called The Business, hosted by Claude Brodesser-Akner.
Their program from March 26, 2007 includes an extended interview with Jerry Ryba, Voiceover agent at CESD. You’ll need to listen through some other material first, but there is so much solid information about voiceover work, especially the big leagues. (My thanks to Nancy Wolfson for alerting me to this interview.)