Instacast for Mac promises to deliver the seamless podcast experience already available on iOS to the desktop.
Macworld has a good review of the beta version of this application.
What’s really fantastic in Instacast is the sync across devices. You can listen to a podcast on your iPhone and resume listening on your iPad exactly where you left.
Having this capability on the Mac too is priceless. I wonder when Apple is going to introduce a similar functionality in iTunes.