You're better off not finding them. The music app on the ipad is broken, especially for podcasts and audiobooks. They have removed a ton of functionality and crippled the app (which was fine in ios 4.x and is fine on iPod touch and iPhones running iOS 5).
I listen to a lot of podcasts, and I used to listen to a lot of them on the iPad, and the music app is comically bad. It's like someone made a list of all the basic functionality found in the app, stripped 75% of it away for no apparent reason, slapped a goofy UI on it and called it a day.