I picked up this term from Doc Searls and his IT Garage (although Dave Winer has been talking about it a lot recently too). The IT Garage link is the more substantial of the two. I've just started to keep my eye on this stuff. (I know it seems odd for a self-proclaimed tech geek like me, but I've yet to pick up an MP3 player).
What's really interesting to me about all this is the capabilities it opens up for the niche markets. Are you an authority on a certain subject? Want to do a weekly or bi-weekly radio show on it? Well, you don't have to scrounge for airtime any longer, because you can now PODcast over the internet. What I'd like to see is some support for Windows Media compatible devices as well. Maybe a plugin for Windows Media Player's using the new MTP (Media Transport Protocol)?
Cool stuff. I've always wanted to do my own computer help/tech show..... Do check out at least the IT Garage link. This is a trend that is really starting to take off, and to me is yet another natural extension of the capabilities of RSS.