Creative has fashioned a portal for their two video player, the Zen Vision and the newly released Zen Vision:M. The site indexes a lot of the popular video and audio podcasts. Additionally they have released a beta version of a software program they are calling ZENCast Organizer. This program will automatically fill up your MP3 player with new content as you subscribe.
I believe that is only compatible with the Vision and Vision:M. It is unclear weather or not the Organizer will be compatible with other players as well. Hopefully it will work with any windows media based digital audio player.