Xcast is a great podcatcher for Mac OS X. With the best iTunes integration that I have seen. Instead of just adding the downloaded content to a playlist, Xcast adds the tracks to iTunes, in the Podcast section, under the correct podcast entry. This allows an it to appear on the iPod in the Podcast section of the UI.
The developer has created a screencast of Xcast, that really shows how well integrated this is with iTunes.
Now, I have told iTunes not to download podcasts, but will do it from Xcast.