This app is great. You can have it discard old podcasts and make sure you only have the lastest ones. It can have it prevent iTune from expiring your unlistened to subscriptions and make sure you have the latest ones. It's fully customizable.

Once you set it up, you can walk away and know that when you sync your iPod or want listen to the latest podcast it will be there for you, and you don't have to worry about filling up your hard disk or iPod. It will remove them according to your rules. Just set it up and forget it.

You can even have it play the latest podcast automatically as it arrives, or use it to wake you up in the morning.

Also, the developer is very responsive and open to improvements.

Give it a try. You'll be glad you did.

Disclosure: I beta tested this version, but am not commercially or otherwise associated with it.