To the best of my knowledge, here is no such thing as an "iTunes-specific" podcast. They may use ipod-formated audio (AAC) or video (MP4), but that can be played back on anything with the correct codecs. Anything DRMed would not technically be a podcast anymore.
Oh trust me, there are some podcasts you can only get via itunes. Most people are cool and just allow direct rss feed access but some screw it up by pushing the rss feed to itunes and then that's the only place you can get it. I was very unhappy with juice as it offten just "went nuts" and tried to download evertything or forget what I had. I'm thinking the best solution is just to have itunes download the most recent podcasts directly to my SD card, it's not EXACTLY what I want, but I'll have to cope.
More over, while most second question has got some amazing attention (thank you all) what about my first is there a good list anywhere of what software will be available at launch? I'm super stoked, I just wanna know what is some icing on the cake.
1. then its not a podcast... they have validity and specifications, just like all rss
2. no one really knows till its ported, but the angstrom repository will give you a good idea of what will probably make it on. there are a few things already set in stone such as firefox and the other basic set of common linux apps