Bringcast, demoed briefly above, is now available in Marketplace. An alternative to the other big pocatcher Podcast!, the software actually allows downloading audio and video podcasts directly to internal storage, unlike the streaming-only version in Podcast!
The software has a built-in database of 100 popular podcasts, more can be added manually, and can download over WIFI or 3G, and also integrates with the music and video hub.
Bringcast is $1.99 and comes with a free trial with only limits the subscriptions to 3 items.
Find it in Marketplace here.