I updated to iTunes 5.0 as soon as I heard about it. Then I booted up my new iTunes, to be told that my Music library had to be recreated for some reason. I thought nothing of it, until I went to the Podcasts list - nothing! I had collected quite a large list of podcasts, only most of which I could remember, and now they were gone!
Or were they? I went to the iTunes Music directory in my ~/Music folder, and found the Podcasts directory. All of the .mp3 files were there. Not only that, but when I dragged the individual folders present in the Podcasts directory onto my iTunes Podcasts window, it recognized the podcasts, and I was able to re-subscribe without any more effort!
Hope this helps somebody out there!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050907195751604