iOS: Castro is one of the better podcast managers on the iPhone, and it's great for those looking for something easy to use. It now offers a little more functionality with a sleep timer, a continuous play option, and a fantastic new playback speed mode.
One of the key features Castro lacked when it first launched was the sleep timer. Now, that's included in the app alongside a continuous play option so you can just let podcasts play out over time. Those are great, but the real hidden improvement here is the new pitch shift algorithm.
Now, when you play a podcast at faster (or slower) speeds, the app runs an algorithm that makes it sound less robotic than other podcast apps. You can get a demo of it here, and if you prefer to listen to podcasts at increased speeds, this is one of the best sounding implementations I've heard. Castro still isn't a full-featured podcast client like Downcast, but for casual podcast listeners, it's the easiest to use.
Castro ($4.99) [iTunes App Store]