Juice (formerly known as iPodder) was the reigning champ. But it's kind of a pain in the behind to get Juice working with Vista. So we're always looking for a better solution.
You can use Miro to download audio podcasts as well as video, but that's sort of like using a tank to drive to the supermarket.
Ziepod, on the other hand, is a bit more like a corvette. It's pretty, easy to use, and fast. The built-in podcast directory is also excellent if you're browsing for new podcasts. Notice we said browsing? There's no search button, which is a bit baffling.
Another odd choice is that while you an set Ziepod to automatically delete podcasts that have been sitting on your PC for a certain period of time, there's no way to customize that setting for different feeds. So if you download some podcasts on a weekly basis and others on a daily basis, there doesn't appear to be an easy way to keep the last 2 days worth of one and 3 weeks worth of the other.
That said, Ziepod does a great job of pulling in your podcasts, storing them, letting you listen on your computer or synchronize with an iPod. There's also a commercial version for $20 with a few additional features like download bandwitdh speed control, and a dockable video bar.