There are a few threads about them, but in a nutshell... Gameroom Junkies is great gameroom discussion, with a lot of pinball talk. Coast2Coast is almost daily shorter shows about hot topics. Spooky Pinball is comedy-based pinball talk with lots of high profile guests. Pinball Soul is sort of like the 'PBS of Pinball Podcasts', the news and information from around the community, about once a month. And The Pinball Podcast is two guys just talking pinball for a few hours. It's probably the greatest and best pinball podcast ever created *cough*not really*cough*. Those are the current shows. BrokenToken is newer, and has mostly been arcade talk with some pin talk.
Of the old shows, This Old Pinball has very in-depth interviews, good stuff. The Silverball is a lot of fun, but is pretty off-topic here and there.