I like the PosCast. It's not strictly baseball, but there's a lot of baseball in there during the season. It's not super serious, but I do enjoy it. Their Christmas Music episode was one of the funniest podcasts I've ever listened to.
Y'all will may be sick of the local yokel's but in season, I really like Grant and Danny's and Dan Kolko's Nats centric podcasts. I don't remember what they're called off hand.