PodcastPickle.comThis is an excellent site for podcast listings.
A lot of people are asking me what a podcast is? If you
check here at Wikipedia, there are some good answers. In short a podcast is an audio file that's on the web, and it's available for download from a website.
So what makes it special is that you can get software (iPodder, or iTunes 4.9, or Odeo's sync, etc.) that will automatically download new 'shows' of the podcasts you subscribe to. Think of it like a newspaper - every day you open the door, and there it is. Like the newspaper, you can take a podcast with you.
This has two killer applications: 1) radio shows that are only on specific times can be listened to at other times, and 2) people can create their own virtual 'radio stations'.
Craigsmusic.net is a great example.
Enjoy!