So I am a little late to the party. I've just found out about podcasts. For a brief description check out Apple's Podcast 101 here.

Wikipedia defines "Podcast" as... Podcasting is the distribution of audio or video files, such as radio programs or music videos, over the internet using either RSS or Atom syndication for listening on mobile devices and personal computers. A podcast is a web feed of audio or video files placed on the Internet for anyone to subscribe to, and also the content of that feed. Podcasters' websites also may offer direct download of their files, but the subscription feed of automatically delivered new content is what distinguishes a podcast from a simple download or real-time streaming. Check out the rest of the definition here.

For an exhaustive list check out the Podcast Directory here. And PodcastAlley.com here.

Instapundit and the InstaWife are now doing podcasts. Check it out http://instapundit.com/archives/028623.php. (Subscription is free!) I've already subscribed.