It's available for Mac, Windows, and Linux; if you're on Debian unstable the installation is as simple as
apt-get install democracyplayer (I uploaded the new packages yesterday, they should have reached all mirrors by now).
If you want to know what this is all about, but you're reluctant to install yet another program, check out this screencast (MOV, 37MB) which shows the basic functionality and user interface and discusses some of the new features... I think you'll like it.
You can use it for all kinds of video blogs and podcasts, it'll download and play almost anything with an RSS feed.
No. Time. To. Blog. But these few lines I wanted to post nevertheless: there's some neat new packages in Debian since today: Nexuiz (nice ego shooter), rcov (code coverage for Ruby), and Democracy Player (RSS video downloader/viewer for videoblogs, packaged by yours truly, as promised).
The video seems to be a bit older, and I have no idea who the original author is or what license applies to it. Anyways, it's funny, scary and very very true at the same time. Watch it.
I was asking myself the same question for a number of reasons lately, and here's what I have found:
As for the content, there's lots of videoblogs out there, and I will blog about that in more detail later on. As an appetizer, you can now subscribe to the new (German) Tagesschau Video Podcast (thanks Tim Pritlove).
Update 2005-11-14: Added Kitty.